Advances in Optical Sensors

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Biosensors biosensors	4.9	6.6	2011	17.1 Days	CHF 2700
Chemosensors chemosensors	3.7	5.0	2013	17.1 Days	CHF 2700
Optics optics	1.1	2.2	2020	19.6 Days	CHF 1200
Photonics photonics	2.1	2.6	2014	14.8 Days	CHF 2400
Sensors sensors	3.4	7.3	2001	16.8 Days	CHF 2600

15 pages, 5733 KiB

Open AccessArticle

Photonic Integrated Circuit Based Temperature Sensor for Out-of-Autoclave Composite Parts Production Monitoring

by Georgios Syriopoulos, Ioannis Poulopoulos, Charalampos Zervos, Evrydiki Kyriazi, Aggelos Poulimenos, Michal Szaj, Jeroen Missinne, Geert van Steenberge and Hercules Avramopoulos

Sensors 2023, 23(18), 7765; https://doi.org/10.3390/s23187765 - 8 Sep 2023

Cited by 7 | Viewed by 1149

Abstract

The use of composite materials has seen widespread adoption in modern aerospace industry. This has been facilitated due to their favourable mechanical characteristics, namely, low weight and high stiffness and strength. For broader implementation of those materials though, the out-of-autoclave production processes have [...] Read more.

The use of composite materials has seen widespread adoption in modern aerospace industry. This has been facilitated due to their favourable mechanical characteristics, namely, low weight and high stiffness and strength. For broader implementation of those materials though, the out-of-autoclave production processes have to be optimized, to allow for higher reliability of the parts produced as well as cost reduction and improved production speed. This optimization can be achieved by monitoring and controlling resin filling and curing cycles. Photonic Integrated Circuits (PICs), and, in particular, Silicon Photonics, owing to their fast response, small size, ability to operate at higher temperatures, immunity to electromagnetic interference, and compatibility with CMOS fabrication techniques, can offer sensing solutions fulfilling the requirements for composite material production using carbon fibres. In this paper, we demonstrate a passive optical temperature sensor, based on a 220 nm height Silicon-on-Insulator platform, embedded in a composite tool used for producing RTM-6 composite parts of high quality (for use in the aerospace industry). The design methodology of the photonic circuit as well as the experimental results and comparison with the industry standard thermocouples during a thermal cycling of the tool are presented. The optical sensor exhibits high sensitivity (85 pm/°C), high linearity (R² = 0.944), and is compatible with the RTM-6 production process, operating up to 180 °C. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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13 pages, 5176 KiB

Open AccessEditor’s ChoiceEssay

Integrated Encapsulation and Implementation of a Linear-Mode APD Detector for Single-Pixel Imaging Lidar

by Akang Lv, Kee Yuan, Jian Huang, Dongfeng Shi, Shiguo Zhang, Yafeng Chen and Zixin He

Photonics 2023, 10(9), 970; https://doi.org/10.3390/photonics10090970 - 24 Aug 2023

Viewed by 1382

Abstract

Single-pixel imaging lidar is a novel technology that leverages single-pixel detectors without spatial resolution and spatial light modulators to capture images by reconstruction. This technique has potential imaging capability in non-visible wavelengths compared with surface array detectors. An avalanche photodiode (APD) is a [...] Read more.

Single-pixel imaging lidar is a novel technology that leverages single-pixel detectors without spatial resolution and spatial light modulators to capture images by reconstruction. This technique has potential imaging capability in non-visible wavelengths compared with surface array detectors. An avalanche photodiode (APD) is a device in which the internal photoelectric effect and the avalanche multiplication effect are exploited to detect and amplify optical signals. An encapsulated APD detector, with an APD device as the core, is the preferred photodetector for lidar due to its high quantum efficiency in the near-infrared waveband. However, research into APD detectors in China is still in the exploratory period, when most of the work focuses on theoretical analysis and experimental verification. This is a far cry from foreign research levels in key technologies, and the required near-infrared APD detectors with high sensitivity and low noise have to be imported at a high price. In this present study, an encapsulated APD detector was designed in a linear mode by integrating a bare APD tube, a bias power circuit, a temperature control circuit and a signal processing circuit, and the corresponding theoretical analysis, circuit design, circuit simulation and experimental tests were carried out. Then, the APD detector was applied in the single-pixel imaging lidar system. The study showed that the bias power circuit could provide the APD with an operating voltage of DC 1.6 V to 300 V and a ripple voltage of less than 4.2 mV. Not only that, the temperature control circuit quickly changed the operating state of the Thermo Electric Cooler (TEC) to stabilize the ambient temperature of the APD and maintain it at 25 ± 0.3 °C within 5 h. The signal processing circuit was designed with a multi-stage amplification cascade structure, effectively raising the gain of signal amplification. By comparison, the trial also suggested that the encapsulated APD detector and the commercial Licel detector had a good agreement on the scattered signal, such as a repetition rate and pulse width response under the same lidar environment. Therefore, target objects in real atmospheric environments could be imaged by applying the encapsulated APD detector to the near-infrared single-pixel imaging lidar system. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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9 pages, 2452 KiB

Open AccessCommunication

Dispersion Turning Attenuation Microfiber for Flowrate Sensing

by Yaqi Tang, Chao Wang, Xuefeng Wang, Meng Jiang, Junda Lao and Dongning Wang

Sensors 2023, 23(16), 7279; https://doi.org/10.3390/s23167279 - 20 Aug 2023

Cited by 3 | Viewed by 1170

Abstract

We demonstrated a new optical fiber modal interferometer (MI) for airflow sensing; the novelty of the proposed structure is that an MI is fabricated based on a piece of HAF, which makes the sensitive MI itself also a hotwire. The interferometer is made [...] Read more.

We demonstrated a new optical fiber modal interferometer (MI) for airflow sensing; the novelty of the proposed structure is that an MI is fabricated based on a piece of HAF, which makes the sensitive MI itself also a hotwire. The interferometer is made by applying arc-discharge tapering and then flame tapering on a 10 mm length high attenuation fiber (HAF, 2 dB/cm) with both ends spliced to a normal single mode fiber. When the diameter of the fiber in the processing region is reduced to about 2 μm, the near-infrared dispersion turning point (DTP) can be observed in the interferometer’s transmission spectrum. Due to the absorption of the HAF, the interferometer will have a large temperature increase under the action of a pump laser. At the same time, the spectrum of the interferometer with a DTP is very sensitive to the change in ambient temperature. Since airflow will significantly affect the temperature around the fiber, this thermosensitive interferometer with an integrated heat source is suitable for airflow sensing. Such an airflow sensor sample with a 31.2 mm length was made and pumped by a 980 nm laser with power up to 200 mW. In the comparative experiment with an electrical anemometer, this sensor exhibits a very high air-flow sensitivity of −2.69 nm/(m/s) at a flowrate of about 1.0 m/s. The sensitivity can be further improved by enlarging the waist length, increasing the pump power, etc. The optical anemometer with an extremely high sensitivity and a compact size has the potential to measure a low flowrate in constrained microfluidic channels. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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13 pages, 9308 KiB

Open AccessArticle

Spatial Spectral Characteristics of Partial Discharge with Different Electrode Models

by Taiqi Wang, Yongkang Cheng, Chao Xu, Haoyu Li, Jiayao Cheng, Gangding Peng and Qiang Guo

Photonics 2023, 10(7), 788; https://doi.org/10.3390/photonics10070788 - 7 Jul 2023

Cited by 3 | Viewed by 1137

Abstract

In this paper, the spatial spectral characteristics of partial discharge (PD) under different electrode models are mainly studied. In the initial corona discharge stage, the emission spectrum is mainly emitted by the N₂(C³II_u→B³II [...] Read more.

In this paper, the spatial spectral characteristics of partial discharge (PD) under different electrode models are mainly studied. In the initial corona discharge stage, the emission spectrum is mainly emitted by the N₂(C³II_u→B³II_g) energy level transition of the N₂ second positive band system. The spectrum is in the ultraviolet range of 294–436 nm, and its main peak is at 337 nm. The streamer discharge stage spectrum is mainly emitted by the energy level transition of the second positive band system of N₂, N⁺, NO, and O⁺ and the first positive band system of N₂(B³II_g→A³

Σ_{u}^{+}

). In the gap of different polarity electrodes, the ultraviolet spectrum content near the positive polarity is more abundant. The UV spectra ranges are 202–225 nm and 229–292 nm, respectively. The discharge of the needle–sphere system is more intense in visible light and near-infrared light, with peaks at 500 nm and 777 nm, respectively. In addition, the PD process based on the finite element method is simulated by COMSOL Multiphysics software. The simulation results show that the distribution of high-energy electron density varies with the electrode spacing and discharge model. The influence of particle energy level transition on the spatial spectral characteristics of PD is verified. This work provides important insights and possibilities for future fluorescent fiberoptic sensing and positioning for spatial PD detection and positioning using spectral characteristic peaks as detection quantities or excitations. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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15 pages, 4194 KiB

Open AccessArticle

Effects of Measurement Temperature on Radioluminescence Processes in Cerium-Activated Silica Glasses for Dosimetry Applications

by Ismail Zghari, Hicham El Hamzaoui, Bruno Capoen, Franck Mady, Mourad Benabdesselam, Géraud Bouwmans, Damien Labat, Youcef Ouerdane, Adriana Morana, Sylvain Girard, Aziz Boukenter and Mohamed Bouazaoui

Sensors 2023, 23(10), 4785; https://doi.org/10.3390/s23104785 - 16 May 2023

Cited by 3 | Viewed by 1375

Abstract

Cerium-doped-silica glasses are widely used as ionizing radiation sensing materials. However, their response needs to be characterized as a function of measurement temperature for application in various environments, such as in vivo dosimetry, space and particle accelerators. In this paper, the temperature effect [...] Read more.

Cerium-doped-silica glasses are widely used as ionizing radiation sensing materials. However, their response needs to be characterized as a function of measurement temperature for application in various environments, such as in vivo dosimetry, space and particle accelerators. In this paper, the temperature effect on the radioluminescence (RL) response of Cerium-doped glassy rods was investigated in the 193–353 K range under different X-ray dose rates. The doped silica rods were prepared using the sol-gel technique and spliced into an optical fiber to guide the RL signal to a detector. Then, the experimental RL levels and kinetics measurements during and after irradiation were compared with their simulation counterparts. This simulation is based on a standard system of coupled non-linear differential equations to describe the processes of electron-hole pairs generation, trapping-detrapping and recombination in order to shed light on the temperature effect on the RL signal dynamics and intensity. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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10 pages, 3674 KiB

Open AccessArticle

Self-Contained Reference Sensors to Reduce Nuisance Alarm Rate in φ-OTDR-Based Fence Intrusion Detection System

by Hailiang Zhang, Hui Dong, Dora Juan Juan Hu and Jun Hong Ng

Optics 2023, 4(2), 330-339; https://doi.org/10.3390/opt4020024 - 15 May 2023

Viewed by 1504

Abstract

Nuisance alarm rate (NAR) is one of the key performance parameters in a phase-sensitive optical time domain reflectometry (φ-OTDR)-based fence intrusion detection system. Typically, the vibrations caused by ambient environmental conditions, such as heavy rain, strong wind, and passing vehicles, easily result in [...] Read more.

Nuisance alarm rate (NAR) is one of the key performance parameters in a phase-sensitive optical time domain reflectometry (φ-OTDR)-based fence intrusion detection system. Typically, the vibrations caused by ambient environmental conditions, such as heavy rain, strong wind, and passing vehicles, easily result in many nuisance alarms. Significant research efforts have been undertaken to suppress the NAR. In this paper, we propose to utilize short segments of the sensing fiber as reference sensors for significant reduction in the NAR in φ-OTDR for the first time, to the best of our knowledge. According to our field trial results, the proposed approach can reduce the NAR by more than 90%. The proposed approach is very simple, practical, and cost-effective, which can be easily integrated with the existing methods of reducing NAR and act as an additional level of decision-making algorithm for triggering alarms. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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(<bold>a</bold>) The schematic diagram of the φ-OTDR system with a reference sensor for fence intrusion detection. (<bold>b</bold>) The schematic diagram of the developed φ-OTDR interrogator. AOM: acousto-optic modulator; CIR: circulator; FUT: fiber under test; PD: photodetector; DAQ: data acquisition card; PC: computer. Full article ">Figure 2
The working principle of the φ-OTDR interrogator with a reference sensor. (<bold>a</bold>) Without strong background vibrations caused by heavy rain or wind, the reference sensor is not triggered; the system alarm threshold is <italic>TH</italic>1. (<bold>b</bold>) With strong background vibrations, the reference sensor is triggered, and the system alarm threshold will be multiplied by <italic>N</italic>, increasing from <italic>TH</italic>1 to <italic>TH</italic>2. (<bold>c</bold>) Algorithm flow chart of the reference sensor working principle. In real-world applications, the proposed approach can be combined with other methods of reducing the NAR. Full article ">Figure 3
(<bold>a</bold>) The fiber cable installation layout on the fences. (<bold>b</bold>) Picture of the sensing fiber cable. Full article ">Figure 4
Waterfall plots of the filtered RB signal for background on a sunny day, three different intrusion events, and background in heavy rain. (<bold>a</bold>) Background on a sunny day; (<bold>b</bold>) fence cutting on a sunny day; (<bold>c</bold>) aided climbing on fence on a sunny day; (<bold>d</bold>) unaided climbing on fence in moderate rain; (<bold>e</bold>) background in heavy rain. Full article ">Figure 5
The RMS values of the alarms for the three types of events. (<bold>a</bold>) Fence cutting on a sunny day; (<bold>b</bold>) aided climbing on fence on a sunny day; (<bold>c</bold>) unaided climbing on fence in moderate rain. Full article ">Figure 6
Alarm records of the field trial without using the reference sensor for 137.5 h. (<bold>a</bold>) The recorded RMS values and times of the alarms generated during the field trial period; the threshold was 150. (<bold>b</bold>) Zoom in of the alarm records induced by heavy rain in the duration from 7:40 to 8:04 on 24 June 2020. (<bold>c</bold>) Probability histogram of the RMS values of the alarms. Full article ">Figure 7
Alarm records of the field trial with using the reference sensor for 294 h. (<bold>a</bold>) All the recorded alarms generated during the field trial period; the threshold <italic>TH</italic>1 was 150, <italic>N</italic> = 2, and the reference sensor threshold <italic>THR</italic> was 110. The red asterisks represent the recorded RMS values of the alarms generated by the fiber mounted on the fences; green curve represents the RMS values of the reference sensor. (<bold>b</bold>) Zoom in of the alarm records in the duration from 7:00 to 13:00 on 12 August 2020. Full article ">Figure 8
RMS values distribution of the alarms in lab tests. (<bold>a</bold>) FUT was 1.9 km SMF. (<bold>b</bold>) FUT was 150 m sensing cable used in the field trials. Full article ">

10 pages, 1031 KiB

Open AccessEditor’s ChoiceCommunication

Single Photon Approach for Chirality Sensing

by Fabrizio Sgobba, Arianna Elefante, Stefano Dello Russo, Mario Siciliani de Cumis and Luigi Santamaria Amato

Photonics 2023, 10(5), 512; https://doi.org/10.3390/photonics10050512 - 28 Apr 2023

Viewed by 1684

Abstract

We developed a high sensitivity optical sensor for circular birefringence using a heralded photon source. The sensor can be employed for chirality measurements and, being based on single photons, can be exploited for fragile biological sample or in metrological applications where the light [...] Read more.

We developed a high sensitivity optical sensor for circular birefringence using a heralded photon source. The sensor can be employed for chirality measurements and, being based on single photons, can be exploited for fragile biological sample or in metrological applications where the light intensity must be kept as low as possible. We found the best operational condition; then, we calibrated the sensor and tested its performance up to a very long acquisition time, obtaining excellent stability and a sub-ppm birefringence detection limit (for a 100 μm sample), thus paving the way for fundamental physics test as well. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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11 pages, 3737 KiB

Open AccessArticle

Hard-Templated Porous Niobia Films for Optical Sensing Applications

by Venelin Pavlov, Rosen Georgiev, Katerina Lazarova, Biliana Georgieva and Tsvetanka Babeva

Photonics 2023, 10(2), 167; https://doi.org/10.3390/photonics10020167 - 4 Feb 2023

Viewed by 1451

Abstract

Porous Nb₂O₅ films obtained by a modified hard-template method were studied and their optical and sensing properties were optimized in order to find applications in chemo-optical sensing. Porous films were prepared by following three steps: liquid mixing of niobium sol [...] Read more.

Porous Nb₂O₅ films obtained by a modified hard-template method were studied and their optical and sensing properties were optimized in order to find applications in chemo-optical sensing. Porous films were prepared by following three steps: liquid mixing of niobium sol and SiO₂ colloids in different volume fractions, thermal annealing of spin-coated films for formation of a rigid niobia matrix, and selective removal of silica phase by wet etching thus generating free volume in the films. The morphology and structure of the films were studied using transmission electron microscopy and selected area electron diffraction, while their optical and sensing properties were estimated using UV-VIS-NIR reflectance measurements in different ambiences such as air, argon and acetone vapors and nonlinear curve fitting of the measured reflectance spectra. Bruggeman effective medium approximation was applied for determination of the volume fraction of silica and air in the films, thus revealing the formation of porosity inside the films. For further characterization of composite films, their water contact angles were measured and finally conclusions about the impact of initial chemical composition and etching duration on properties of the films were drawn. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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TEM pictures of SiO2 particles in Ludox® (a) and histogram distribution of their size (b). Full article ">Figure 2
TEM images of porous films of Nb2O5 prepared by mixing Nb sol and a colloidal solution of nanoparticles of SiO2 (commercially available LUDOX®) in different volume fractions: 50:1 (a), 20:1 (b), 10:1 (c) and 5:1 (d); Typical selected area electron diffraction (SAED) pattern is shown as an inset. Full article ">Figure 3
Dispersion of refractive index of Nb2O5 films prepared by mixing of Nb sol and colloidal solution of nanoparticles of SiO2 in different volume fractions indicated in the figure. Full article ">Figure 4
Reflectance spectra of hard-templated Nb2O5 obtained by liquid-phase mixing of Nb sol and silica colloids in volume ratios of 50:1 (a), 20:1 (b), 10:1 (c) and 5:1 (d) during selective removal of SiO2 phase by wet-etching. Full article ">Figure 5
Refractive index change as a function of etching time of porous Nb2O5 layers obtained by liquid phase mixing of niobium sol and colloidal solution of SiO2 nanoparticles in different volume ratios indicated in the figure. Full article ">Figure 6
Water contact angles of hard-templated Nb2O5 films obtained by liquid phase mixing of Nb sol and silica colloids in different volume ratios indicated in the figure. Full article ">Figure 7
Water contact angles as a function of etching time of hard-templated porous Nb2O5 films obtained by liquid phase mixing of Nb sol and silica colloids in different volume ratios indicated in the figure. Water contact angles of pure Ludox® and niobia films are represented by the two dashed horizontal lines. Full article ">Figure 8
Refractive index change due to acetone vapor absorption prior to and after selective removal of silica in hard-templated films of Nb2O5 obtained by liquid phase mixing of Nb sol and silica colloids in different volume ratios indicated in the figure. The films were etched in a standard SiO2 etcher for different times: 240 s for the 50:1 and 20:1 films, 210 s for the 10:1 film and 120 s for the 5:1 film. Full article ">Figure 9
Refractive index change as a function of etching time of hard-templated films of Nb2O5 obtained by liquid phase mixing of Nb sol and silica colloids in different volume ratios indicated in the figure. Full article ">

10 pages, 3886 KiB

Open AccessCommunication

An Ultracompact Angular Displacement Sensor Based on the Talbot Effect of Optical Microgratings

by Zhiyong Yang, Xiaochen Ma, Daguo Yu, Bin Cao, Qianqi Niu, Mengwei Li and Chenguang Xin

Sensors 2023, 23(3), 1091; https://doi.org/10.3390/s23031091 - 17 Jan 2023

Cited by 4 | Viewed by 1800

Abstract

Here, we report an ultracompact angular displacement sensor based on the Talbot effect of optical microgratings. Periodic Talbot interference patterns were obtained behind an upper optical grating. By putting another grating within the Talbot region, the total transmission of the two-grating structure was [...] Read more.

Here, we report an ultracompact angular displacement sensor based on the Talbot effect of optical microgratings. Periodic Talbot interference patterns were obtained behind an upper optical grating. By putting another grating within the Talbot region, the total transmission of the two-grating structure was found to be approximatively in a linear relationship with the relative pitch angle between the two gratings, which was explained by a transversal shift of the Talbot interference patterns. The influence of the grating parameters (e.g., the grating period, the number of grating lines and the gap between the two gratings) was also studied in both a simulation and an experiment, showing a tunable sensitivity and range by simply changing the grating parameters. A sensitivity of 0.19 mV/arcsec was experimentally obtained, leading to a relative sensitivity of 0.27%/arcsec within a linear range of ±396 arcsec with the 2 μm-period optical gratings. Benefitting from tunable properties and an ultracompact structure, we believe that the proposed sensor shows great potential in applications such as aviation, navigation, robotics and manufacturing engineering. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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18 pages, 2143 KiB

Open AccessArticle

Remote Non-Invasive Fabry-Pérot Cavity Spectroscopy for Label-Free Sensing

by Abeer Al Ghamdi, Benjamin Dawson, Gin Jose and Almut Beige

Sensors 2023, 23(1), 385; https://doi.org/10.3390/s23010385 - 29 Dec 2022

Cited by 2 | Viewed by 2245

Abstract

One way of optically monitoring molecule concentrations is to utilise the high sensitivity of the transmission and reflection rates of Fabry-Pérot cavities to changes of their optical properties. Up to now, intrinsic and extrinsic Fabry-Pérot cavity sensors have been considered with analytes either [...] Read more.

One way of optically monitoring molecule concentrations is to utilise the high sensitivity of the transmission and reflection rates of Fabry-Pérot cavities to changes of their optical properties. Up to now, intrinsic and extrinsic Fabry-Pérot cavity sensors have been considered with analytes either being placed inside the resonator or coupled to evanescent fields on the outside. Here we demonstrate that Fabry-Pérot cavities can also be used to monitor molecule concentrations non-invasively and remotely, since the reflection of light from the target molecules back into the Fabry-Pérot cavity adds upwards peaks to the minima of its overall reflection rate. Detecting the amplitude of these peaks reveals information about molecule concentrations. By using an array of optical cavities, a wide range of frequencies can be probed at once and a unique optical fingerprint can be obtained. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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12 pages, 4709 KiB

Open AccessCommunication

Fossil Plant Remains Diagnostics by Laser-Induced Fluorescence and Raman Spectroscopies

by Alexey F. Bunkin, Sergey M. Pershin, Diana G. Artemova, Sergey V. Gudkov, Alexey V. Gomankov, Pavel A. Sdvizhenskii, Mikhail Ya. Grishin and Vasily N. Lednev

Photonics 2023, 10(1), 15; https://doi.org/10.3390/photonics10010015 - 24 Dec 2022

Cited by 2 | Viewed by 1952

Abstract

Fossilized plant remains have been studied simultaneously by laser induced fluorescence and Raman spectroscopies, to reveal the prospective methods for onsite or/and laser remote sensing in future extraterrestrial missions. A multiwavelength instrument, capable of fluorescence and Raman measurements, has been utilized for the [...] Read more.

Fossilized plant remains have been studied simultaneously by laser induced fluorescence and Raman spectroscopies, to reveal the prospective methods for onsite or/and laser remote sensing in future extraterrestrial missions. A multiwavelength instrument, capable of fluorescence and Raman measurements, has been utilized for the study of isolated plant fossils, as well as fossils associated with sedimentary rocks. Laser-induced fluorescence spectroscopy revealed that plant fossils and rocks’ luminosity differed significantly due to chlorophyll derivatives (chlorin, porphyrins, lignin components etc.); therefore, fossilized plants can be easily detected at rock surfaces onsite. Raman spectroscopy highly altered the fossilized graphitic material via the carbon D and G bands. Our results demonstrated that combined laser-induced fluorescence and Raman spectroscopy measurements can provide new insights into the detection of samples with biogenicity indicators such as chlorophyll and its derivatives, as well as kerogenous materials. The prospects of multiwavelength LIDAR instrument studies under fieldwork conditions are discussed for fossils diagnostics. The method of laser remote sensing can be useful in geological exploration in the search for oil, coal-bearing rocks, and rocks with a high content of organic matter. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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(a)—Fluorescence spectra map for isolated plant fossil sample No 1865/3; (b)—fossil sample No 1865/3 and Spectralon® fluorescence spectra comparison with the 305 nm excitation. Full article ">Figure 2
Laser-induced fluorescence spectra of (1) Ginkgo biloba cuticle, (2) rock sample No 4552/18, and (3) rock sample No 4388/563. Full article ">Figure 3
Laser fluorescence spectra of (1) Ginkgo biloba leaf cuticle, (2) Phylladoderma (Aequistomia) annulata cuticle (sample No 4552/700-B), and (3) dry untreated leaf of Ginkgo biloba. Full article ">Figure 4
Laser fluorescence spectra of (1) rock sample No 4552/18 and (2) fossilized material of Tatarina conspicua leaf (the same sample No 4552/18). Full article ">Figure 5
Laser fluorescence spectra of (1) rock sample No 4388/563 and (2) Tatarina conspicua leaf impression with fossilized material residues (the same sample No 4388/563). Full article ">Figure 6
Pulsed Raman spectra of fossilized sample 1865/3 and 1864_29 samples measured by LIDAR with 532 nm excitation. Spectra are summed for 1000 laser pulses to improve signal-to-noise ratio. Full article ">Figure 7
Continuous wave Raman spectra of isolated fossilized material 1865/3 (a) and 1864_29 samples at the mudstone (b) measured by Enspectra R532 with 532 nm. (The mudstone rock Raman spectrum was multiplied 2-fold for better view). Spectra were acquired with the 180 s gate and were corrected on background emission. Full article ">

13 pages, 6891 KiB

Open AccessArticle

Carbon Monoxide Detection Based on the Carbon Nanotube-Coated Fiber Gas Sensor

by Yin Zhang, Wenwen Yu, Dibo Wang, Ran Zhuo, Mingli Fu and Xiaoxing Zhang

Photonics 2022, 9(12), 1001; https://doi.org/10.3390/photonics9121001 - 19 Dec 2022

Cited by 3 | Viewed by 2274

Abstract

Accurate detection of the internal decomposition components of SF₆ electrical equipment plays an important role in the evaluation of equipment status. However, gas samples are usually taken out for detection at present, which makes it difficult to understand the real situation inside [...] Read more.

Accurate detection of the internal decomposition components of SF₆ electrical equipment plays an important role in the evaluation of equipment status. However, gas samples are usually taken out for detection at present, which makes it difficult to understand the real situation inside the equipment. In this paper, a carbon nanotube-coated fiber gas sensor is proposed, which has the potential to be applied as a built-in gas sensor. The fiber loop ring-down (FLRD) gas detection system based on the carbon nanotube-coated fiber gas sensor was built, and the detectable decomposition components among the four typical SF₆ decomposition components of SO₂, SO₂F₂ and SOF₂ and CO were analyzed. The results showed that the fiber gas sensor was most sensitive to CO. Based on density functional theory, it was found that single-walled carbon nanotubes had the best adsorption effect on CO molecules under the same conditions, with the adsorption energy reaching −0.150 Ha. The detection performance of the system for CO was studied, and the results showed that there was a good linear relationship between CO concentration and ring-down time: R² was 0.984, the maximum inversion error of 0~200 ppm CO was 1.916 ppm, and the relative error was 4.10%. The sensitivity of the system was 0.183 ns/ppm, and the detection limit of the system was 19.951 ppm. The system had good stability, with the standard deviation of single-point repeatability being 0.00356, and the standard deviation of the long period of the experiment being 0.00606. The research results provide a new idea for the detection of SF₆ decomposition components, and lay the foundation for the component detection method of built-in fiber sensor of SF₆ electrical equipment. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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11 pages, 2613 KiB

Open AccessCommunication

Overcoming the Lead Fiber-Induced Limitation on Pulse Repetition Rate in Distributed Fiber Sensors

by Hailiang Zhang, Hui Dong, Dora Juan Juan Hu and Jianzhong Hao

Photonics 2022, 9(12), 965; https://doi.org/10.3390/photonics9120965 - 10 Dec 2022

Cited by 2 | Viewed by 1417

Abstract

Distributed fiber sensor (DFS)-based dynamic sensing has attracted increasing attention thanks to the growing demand in areas such as structural health monitoring and geophysical science. The maximum detectable frequency of DFSs depends on the maximum pulse repetition rate (MPRR), which is limited by [...] Read more.

Distributed fiber sensor (DFS)-based dynamic sensing has attracted increasing attention thanks to the growing demand in areas such as structural health monitoring and geophysical science. The maximum detectable frequency of DFSs depends on the maximum pulse repetition rate (MPRR), which is limited by the total length of the fiber under test (FUT). In some real-world applications, there is some distance between the interrogator and the monitoring site. Therefore, only a small part of the FUT acts as a sensing fiber (SF), while the other major part just acts as a lead fiber (LF), and the MPRR is limited by the LF and SF. Overcoming the LF-induced extra limitation on the MPRR is a practical problem for many DFS applications. In this paper, to the best of our knowledge, we propose a simple approach for overcoming the LF-induced extra limitation on the MPRR by dividing the DFS interrogator into two parts, for the first time. The proposed approach can be easily implemented for the real-world applicationsof DFSs whose LF is much longer than SF. It has been experimentally validated by using conventional phase-sensitive optical time domain reflectometry and Brillouin optical time domain analysis. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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Schematic diagram of experimental setup for monitoring the dynamic strain of the basin ship model. Full article ">Figure 2
Schematic diagram of ϕ-OTDR system. The gray dashed rectangle and red dashed rectangle show the difference between the conventional ϕ-OTDR system and our proposed one. Points “a” and “b” represent the connection points. In the conventional setup, the CIR is inside of the interrogator, and FUT = LF + SF. In our proposed setup, CIR is moved to the sensing site from the interrogator, and FUT = SF. AOM: acousto-optic modulator, CIR: circulator, PD: photodetector, DAQ: data acquisition card. LF: lead fiber, SF: sensing fiber. Full article ">Figure 3
Experimental results of using conventional ϕ-OTDR setup, the total length of the FUT was about 12.5 km. (a) Measured incorrect ϕ-OTDR traces while filtering out the low-frequency components when the pulse repetition rate was 40 kHz. (b) Frequency spectrum of the measured incorrect signal located at 12,445 m, which was within the PZT zone. Full article ">Figure 4
Experimental results of using the proposed ϕ-OTDR setup. (a) Measured correct ϕ-OTDR traces corresponding to the 2.19 km SF while filtering out the low-frequency components when the pulse repetition rate was 40 kHz, the location of PZT zone on the SF was the same as that in <a href="#photonics-09-00965-f003" class="html-fig">Figure 3</a>a. (b) Frequency spectrum of the measured signal located at 2195 m (the same location as <a href="#photonics-09-00965-f003" class="html-fig">Figure 3</a>b, 2195 m + LF = 12,445 m) within the PZT zone. Full article ">Figure 5
Schematic diagram of BOTDA setup. The gray dashed rectangle and red dashed rectangle show the difference between the conventional BOTDA system and our proposed one. Points “a”, “b” and “c” represent the connection points. In conventional setup, the OI and CIR are inside of the interrogator, and FUT = LF1 + SF + LF2. In our proposed setup, the OI and CIR are moved to the sensing site from the interrogator, and FUT = SF. OC: optical coupler; EOM: electro-optic modulator; VOA: variable optical attenuator; OI: optical isolator; LF1: lead fiber 1; LF2: lead fiber 2; LF3: lead fiber 3; SF: sensing fiber; CIR: circulator; EDFA: erbium-doped fiber amplifier PD: photodetector, DAQ: data acquisition card. Full article ">Figure 6
Experimental results of using the proposed BOTDA setup. (a) Measured BGS distribution along the sensing fiber. (b) Extracted strain distribution along the sensing fiber. Full article ">Figure 7
Comparison between the conventional and our proposed BOTDA systems when the interrogator is close to the sensing zone. Points “a”, “b” and “c” represent the connection points. (a) Conventional BOTDA system, in which the OI and CIR are integrated into the interrogator. (b) By using our proposed approach, the OI and CIR are installed on-site. OI: optical isolator; CIR: circulator. Full article ">

9 pages, 6658 KiB

Open AccessCommunication

Fluorescence Mapping of Agricultural Fields Utilizing Drone-Based LIDAR

by Vasily N. Lednev, Mikhail Ya. Grishin, Pavel A. Sdvizhenskii, Rashid K. Kurbanov, Maksim A. Litvinov, Sergey V. Gudkov and Sergey M. Pershin

Photonics 2022, 9(12), 963; https://doi.org/10.3390/photonics9120963 - 10 Dec 2022

Cited by 7 | Viewed by 2036

Abstract

A compact and low-weight LIDAR instrument has been developed for laser-induced fluorescence spectroscopy sensing of maize fields. Fluorescence LIDAR had to be installed on a small industrial drone so that its mass was <2 kg and power consumption was <5 W. The LIDAR [...] Read more.

A compact and low-weight LIDAR instrument has been developed for laser-induced fluorescence spectroscopy sensing of maize fields. Fluorescence LIDAR had to be installed on a small industrial drone so that its mass was <2 kg and power consumption was <5 W. The LIDAR instrument utilized a continuous wave diode laser (405 nm, 150 mW) for inducing fluorescence and a small spectrometer for backscattered photons acquisition. For field testing, the LIDAR instrument was installed on a quadcopter for remote sensing of plants in a maize field in three periods of the plant’s life. The obtained fluorescence signal maps have demonstrated that the average chlorophyll content is rather non-uniform over the field and tends to increase through the plant vegetation cycle. Field tests proved the feasibility and perspectives of autonomous LIDAR sensing of agricultural fields from drones for the detection and location of plants under stress. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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15 pages, 3841 KiB

Open AccessArticle

Au Nanoparticles (NPs) Decorated Co Doped ZnO Semiconductor (Co₄₀₀-ZnO/Au) Nanocomposites for Novel SERS Substrates

by Yan Zhai, Xiaoyu Zhao, Zhiyuan Ma, Xiaoyu Guo, Ying Wen and Haifeng Yang

Biosensors 2022, 12(12), 1148; https://doi.org/10.3390/bios12121148 - 8 Dec 2022

Cited by 2 | Viewed by 2475

Abstract

Au nanoparticles were decorated on the surface of Co-doped ZnO with a certain ratio of Co²⁺/Co³⁺ to obtain a novel semiconductor-metal composite. The optimal substrate, designated as Co₄₀₀-ZnO/Au, is beneficial to the promotion of separation efficiency of electron [...] Read more.

Au nanoparticles were decorated on the surface of Co-doped ZnO with a certain ratio of Co²⁺/Co³⁺ to obtain a novel semiconductor-metal composite. The optimal substrate, designated as Co₄₀₀-ZnO/Au, is beneficial to the promotion of separation efficiency of electron and hole in a semiconductor excited under visible laser exposure, which the enhances localized surface plasmon resonance (LSPR) of the Au nanoparticles. As an interesting finding, during Co doping, quantum dots of ZnO are generated, which strengthen the strong semiconductor metal interaction (SSSMI) effect. Eventually, the synergistic effect effectively advances the surface enhancement Raman scattering (SERS) performance of Co₄₀₀-ZnO/Au composite. The enhancement mechanism is addressed in-depth by morphologic characterization, UV-visible, X-ray diffraction, photoluminescence, X-ray photoelectron spectroscopy, density functional theory, and finite difference time domain (FDTD) simulations. By using Co₄₀₀-ZnO/Au, SERS detection of Rhodamine 6G presents a limit of detection (LOD) of 1 × 10⁻⁹ M. As a real application, the Co₄₀₀-ZnO/Au-based SERS method is utilized to inspect tyramine in beer and the detectable concentration of 1 × 10⁻⁸ M is achieved. In this work, the doping strategy is expected to realize a quantum effect, triggering a SSSMI effect for developing promising SERS substrates in future. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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13 pages, 3351 KiB

Open AccessArticle

Highly Sensitive Zinc Oxide Fiber-Optic Biosensor for the Detection of CD44 Protein

by Zhaniya U. Paltusheva, Zhannat Ashikbayeva, Daniele Tosi and Lesya V. Gritsenko

Biosensors 2022, 12(11), 1015; https://doi.org/10.3390/bios12111015 - 14 Nov 2022

Cited by 8 | Viewed by 2310

Abstract

Currently, significant progress is being made in the prevention, treatment and prognosis of many types of cancer, using biological markers to assess current physiological processes in the body, including risk assessment, differential diagnosis, screening, treatment determination and monitoring of disease progression. The interaction [...] Read more.

Currently, significant progress is being made in the prevention, treatment and prognosis of many types of cancer, using biological markers to assess current physiological processes in the body, including risk assessment, differential diagnosis, screening, treatment determination and monitoring of disease progression. The interaction of protein coding gene CD44 with the corresponding ligands promotes the processes of invasion and migration in metastases. The study of new and rapid methods for the quantitative determination of the CD44 protein is essential for timely diagnosis and therapy. Current methods for detecting this protein use labeled assay reagents and are time consuming. In this paper, a fiber-optic biosensor with a spherical tip coated with a thin layer of zinc oxide (ZnO) with a thickness of 100 nm, deposited using a low-cost sol–gel method, is developed to measure the CD44 protein in the range from 100 aM to 100 nM. This sensor is easy to manufacture, has a good response to the protein change with detection limit of 0.8 fM, and has high sensitivity to the changes in the refractive index (RI) of the environment. In addition, this work demonstrates the possibility of achieving sensor regeneration without damage to the functionalized surface. The sensitivity of the obtained sensor was tested in relation to the concentration of the control protein, as well as without antibodies—CD44. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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Figure 1
Experimental setup for the detection of the CD44 protein using a biofunctionalized sensor. Full article ">Figure 2
Design and calibration of the ball resonator biosensor: (a) two-sided profilometry of the ball resonator, measured through the CO2 laser splicer; (b) 3D mesh of the ball resonator, highlighting the longitudinal cross-sections (grey) and azimuthal planes (purple); (c) S-polarization spectrum of the bare ball resonator sensor, measured for different RI values ranging from 1.351 to 1.360; (d) the inset shows the spectral feature around 1567 nm used for spectral tracking of the intensity; (e) RI calibration, showing the change of intensity as a function of the RI change and sensitivity estimation (−80.056 dB/RIU). Full article ">Figure 3
Morphological analysis of the surface of the ball resonator optical fiber coated with a ZnO layer: (a) SEM image of the optical fiber sensor showing its spherical shape and surface coating; (b) SEM image demonstrating the grain structure of the ZnO layer; (c) ZnO layer thickness on the surface of the optical fiber biosensor; (d) TEM image of ZnO; (e) EDS—surface analysis of the ball resonator optical fibers demonstrating the presence of Zn, O, C, and Si elements. Full article ">Figure 4
(a) X-ray diffraction pattern of ZnO layer; (b) FT-IR spectrum of ZnO layer. Full article ">Figure 5
Detection of CD44 using the biofunctionalized sensor: (a) reflective spectrum of the biosensor; (b) the S-polarization spectrum is chosen for interrogation; (c) the inset shows the spectral portion in correspondence to the main dip; interrogation can be performed by tracking either the intensity change ΔA or the wavelength shift Δλ; (d,e) CD44 protein detection charts, reporting the wavelength shift (d) and the intensity change (e); (f) sensorgram for the CD44 detection, reporting the instantaneous wavelength (markers) and average (solid lines) over 109 min with 1-min sampling. Full article ">Figure 6
Evaluation of specificity, repeatability, and regeneration of the biosensor: (a) the specificity was estimated by comparing the response of the CD44 biosensor from the reference value, for every concentration within 1 fM and 10 nM, to two additional ball resonator sensors fabricated with the same method and having a similar sensitivity and interrogation process. Negative control = biosensor with no antibodies; PSA control = CD44-biosensor detecting different contrations of PSA. Error bars = ±standard deviation reported over 11 consecutive measurements; (b) repeatability of the whole biosensing device; the chart compares the normalized response, in terms of intensity change, for 3 different ball resonator biosensors fabricated and interrogated with the same method, responding to CD44 concentrations. Furthermore, 0–100% normalized values account for the response of the sensor at 1 fM (≈LoD) and 100 nM, respectively. Solid line = average, shadowed region = ±standard deviation for 3 different sensors with same biofunctionalization; markers show individual data points; (c) regeneration of the biosensor: the chart displays the response of the same biosensor in the first measurement, compared with the sensor regenerated once (red) and twice (green). Full article ">

9 pages, 2531 KiB

Open AccessArticle

Sagnac Interferometric Temperature Sensor Based on Boron-Doped Polarization-Maintaining Photonic Crystal Fibers

by Lan Cheng, Jun Liang, Shiwei Xie and Yilin Tong

Optics 2022, 3(4), 400-408; https://doi.org/10.3390/opt3040034 - 5 Nov 2022

Cited by 2 | Viewed by 1380

Abstract

A sensitive temperature sensor was demonstrated using boron-doped polarization-maintaining photonic crystal fiber (PM-PCF) as a Sagnac interferometer (SI). This boron-doped PM-PCF combines both the geometric birefringence introduced by the PCF structure design and the stress birefringence introduced by the boron-doped stress-applying parts. However, [...] Read more.

A sensitive temperature sensor was demonstrated using boron-doped polarization-maintaining photonic crystal fiber (PM-PCF) as a Sagnac interferometer (SI). This boron-doped PM-PCF combines both the geometric birefringence introduced by the PCF structure design and the stress birefringence introduced by the boron-doped stress-applying parts. However, we found that the stress birefringence dominates the total birefringence of the sensor by numerical analysis. In the experiments, the fabricated sensor exhibited the highest temperature sensitivity of −1.83 nm/°C within the wide temperature range of 28~76 °C. The temperature sensitivity was mainly derived from the stress birefringence of boron-doped PM-PCF SI. These findings provide some support for the designation of high-precision temperature sensors. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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12 pages, 4412 KiB

Open AccessArticle

A High-Detection-Efficiency Optoelectronic Device for Trace Cadmium Detection

by Huangling Gu and Long Wang

Sensors 2022, 22(15), 5630; https://doi.org/10.3390/s22155630 - 28 Jul 2022

Cited by 1 | Viewed by 2033

Abstract

Cadmium (Cd) pollution in soil is a serious threat to food security and human health, while, currently, the most widely used detection methods cannot accurately reflect the content of heavy metals in soil. Soil heavy metal detection combined with microelectronic sensors has become [...] Read more.

Cadmium (Cd) pollution in soil is a serious threat to food security and human health, while, currently, the most widely used detection methods cannot accurately reflect the content of heavy metals in soil. Soil heavy metal detection combined with microelectronic sensors has become an important means of environmental heavy metal pollution prevention and control. X-ray Fluorescence spectrometry (XRF) can capture the excitation spectrum of metal elements, which is often used to detect Cd (II). However, due to the lack of high-performance optoelectronic devices, the analysis accuracy of the system cannot meet the requirements. Therefore, this study proposes a high-detection-efficiency photodiode (HDEPD) which can effectively improve the detection accuracy of the analyzer. The HDEPD is manufactured based on a 0.18 μm standard complementary metal-oxide-semiconductor (CMOS) process. The volt-ampere curve, spectral response and noise characteristics of the device are obtained by constructing a test circuit combined with a spectral detection system. The test results show that the threshold voltage of HDEPD is 12.15 V. When the excess bias voltage increases from 1 V to 3 V, the spectral response peak of the device appears at 500 nm, and the photon detection probability (PDP) increases from 41.7% to 52.8%. The dark count rate (DCR) is 31.9 Hz/μm² at a 3 V excess bias voltage. Since the excitation spectrum peak of Cd (II) is between 500 nm and 600 nm, the wavelength response range of HDEPD fully meets the detection requirements of Cd (II). Full article

(This article belongs to the Topic Advances in Optical Sensors)

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18 pages, 5681 KiB

Open AccessArticle

Study on Quantitative Characterization of Coupling Effect between Mining-Induced Coal-Rock Mass and Optical Fiber Sensing

by Wengang Du, Jing Chai, Dingding Zhang, Yibo Ouyang and Yongliang Liu

Sensors 2022, 22(13), 5009; https://doi.org/10.3390/s22135009 - 2 Jul 2022

Cited by 3 | Viewed by 1627

Abstract

The monitoring of mine pressure, division of vertical zoning of the overburden, discrimination of key stratum structure of the overburden and monitoring of advanced abutment pressure are still the main research problems in the field of coal mining. Therefore, the promotion of development [...] Read more.

The monitoring of mine pressure, division of vertical zoning of the overburden, discrimination of key stratum structure of the overburden and monitoring of advanced abutment pressure are still the main research problems in the field of coal mining. Therefore, the promotion of development of a monitoring technology of mining-induced rock mass deformation has important research value in the mining field. There are many problems to be solved in the application of optical fiber sensing (OFS) to deformation monitoring, such as the corresponding relationship between actual deformation and optical parameters, the coupling relationship between the optical fiber and rock mass and the reasonable division of vertical zoning of the overburden. In this study, a quantitative index of coupling action between the mining rock mass and optical fiber is put forward, and the coupling coefficient of different vertical zonings is quantitatively analyzed and discussed. Based on this, five different media in contact with optical fiber are proposed. The relationship between the strain curve form, the development height of the fracture zone and the activity of key stratum is established. It is of great academic value and research significance to establish a characterization system of displacement, deformation and structural evolution of overlying strata based on optical fiber sensing technology. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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13 pages, 2582 KiB

Open AccessArticle

A Combined Near-Infrared and Mid-Infrared Spectroscopic Approach for the Detection and Quantification of Glycine in Human Serum

by Thulya Chakkumpulakkal Puthan Veettil and Bayden R. Wood

Sensors 2022, 22(12), 4528; https://doi.org/10.3390/s22124528 - 15 Jun 2022

Cited by 10 | Viewed by 2889

Abstract

Serum is an important candidate in proteomics analysis as it potentially carries key markers on health status and disease progression. However, several important diagnostic markers found in the circulatory proteome and the low-molecular-weight (LMW) peptidome have become analytically challenging due to the high [...] Read more.

Serum is an important candidate in proteomics analysis as it potentially carries key markers on health status and disease progression. However, several important diagnostic markers found in the circulatory proteome and the low-molecular-weight (LMW) peptidome have become analytically challenging due to the high dynamic concentration range of the constituent protein/peptide species in serum. Herein, we propose a novel approach to improve the limit of detection (LoD) of LMW amino acids by combining mid-IR (MIR) and near-IR spectroscopic data using glycine as a model LMW analyte. This is the first example of near-IR spectroscopy applied to elucidate the detection limit of LMW components in serum; moreover, it is the first study of its kind to combine mid-infrared (25–2.5 μm) and near-infrared (2500–800 nm) to detect an analyte in serum. First, we evaluated the prediction model performance individually with MIR (ATR-FTIR) and NIR spectroscopic methods using partial least squares regression (PLS-R) analysis. The LoD was found to be 0.26 mg/mL with ATR spectroscopy and 0.22 mg/mL with NIR spectroscopy. Secondly, we examined the ability of combined spectral regions to enhance the detection limit of serum-based LMW amino acids. Supervised extended wavelength PLS-R resulted in a root mean square error of prediction (RMSEP) value of 0.303 mg/mL and R² value of 0.999 over a concentration range of 0–50 mg/mL for glycine spiked in whole serum. The LoD improved to 0.17 mg/mL from 0.26 mg/mL. Thus, the combination of NIR and mid-IR spectroscopy can improve the limit of detection for an LMW compound in a complex serum matrix. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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Figure 1
Conceptual representation of experiment and associated chemometrics. Full article ">Figure 2
(a) Second derivatized spectra of fused ATR–NIR datasets of dried glycine deposits in 12,500–1350 nm region. Magnified view of (b) NIR region (2500–1350 nm) and (c) mid-IR region (1600–800 cm−1). Important bands in the spectra are labeled. Full article ">Figure 3
(a) Baseline corrected raw spectra of glycine-spiked human serum samples. The concentration of glycine ranges from 0–50 mg/mL. (b) Magnified view of 2500–2000 nm region where major contribution from glycine is observed. Full article ">Figure 4
PLS-R predicted model of glycine-spiked serum samples. (a) Regression plot of entire range between 0 (control) and 50 mg/mL region. (b) Extrapolated and remodeled 0–2.5 mg/mL region. (c) Corresponding regression coefficient/vector over hetero-spectral region covering NIR (2500–1350 nm) and MIR (12,500–5555 nm). (d) Magnified view of regression vector over 2500–1350 nm and (e) 12,500–5555 nm region. Full article ">Figure 5
PCR predicted model of glycine-spiked serum samples. (a) Regression plot of entire range between 0 (control) and 50 mg/mL region. (b) Extrapolated and remodeled 0–2.5 mg/mL region. (c) Corresponding regression coefficient/vector over hetero-spectral region covering NIR (2500–1350 nm) and MIR (1800–800 cm−1). (d) Magnified view of regression vector over 2500–1350 nm and (e) scores plot between PC1 and PC2. Full article ">

12 pages, 2687 KiB

Open AccessArticle

Terahertz Metamaterial Sensor for Sensitive Detection of Citrate Salt Solutions

by Xinxin Deng, Yanchun Shen, Bingwei Liu, Ziyu Song, Xiaoyong He, Qinnan Zhang, Dongxiong Ling, Dongfeng Liu and Dongshan Wei

Biosensors 2022, 12(6), 408; https://doi.org/10.3390/bios12060408 - 13 Jun 2022

Cited by 29 | Viewed by 3189

Abstract

Citrate salts (CSs), as one type of organic salts, have been widely used in the food and pharmaceutical industries. Accurate and quantitative detection of CSs in food and medicine is very important for health and safety. In this study, an asymmetric double-opening ring [...] Read more.

Citrate salts (CSs), as one type of organic salts, have been widely used in the food and pharmaceutical industries. Accurate and quantitative detection of CSs in food and medicine is very important for health and safety. In this study, an asymmetric double-opening ring metamaterial sensor is designed, fabricated, and used to detect citrate salts combined with THz spectroscopy. Factors that influence the sensitivity of the metamaterial sensor including the opening positions and the arrangement of the metal opening ring unit, the refraction index and the thickness of the analyte deposited on the metamaterial sensor were analyzed and discussed from electromagnetic simulations and THz spectroscopy measurements. Based on the high sensitivity of the metamaterial sensor to the refractive index of the analyte, six different citrate salt solutions with low concentrations were well identified. Therefore, THz spectroscopy combined with a metamaterials sensor can provide a new, rapid, and accurate detection of citrate salts. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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Figure 1
Schematic diagrams of the asymmetric metal ring unit with two openings at a changing angle of Δθ (a) and the asymmetric metal ring array at a rotation angle of φ = 40° (b). The THz wave TE incidence is indicated in the inset of (a). Full article ">Figure 2
Transmission spectra of the metamaterial sensor with different changing angles (a) and with different rotation angles (b). Full article ">Figure 3
Optical microscope image of the sensor. Full article ">Figure 4
(a) Transmission spectra of the simulated metamaterial sensor covered by analytes with different refractive indices at h = 20 μm; (b) variation in the resonant peak frequency shift with the refractive index of the analyte; (c) transmission spectra of the simulated metamaterial sensor covered by analytes with different thicknesses at n = 1.8; (d) variation in the resonant peak frequency shift with the thickness of the analyte. Full article ">Figure 5
Measured and simulated THz transmission spectra of the blank sensor without analytes. Full article ">Figure 6
Transmission spectral curves of the blank sensor and the sensor covered with six different CSs. Full article ">Figure 7
Refractive indices of CSs measured by THz–TDS system. Full article ">

10 pages, 1629 KiB

Open AccessArticle

Charge-Sensitive Optical Detection of Binding Kinetics between Phage-Displayed Peptide Ligands and Protein Targets

by Runli Liang, Yingnan Zhang, Guangzhong Ma and Shaopeng Wang

Biosensors 2022, 12(6), 394; https://doi.org/10.3390/bios12060394 - 8 Jun 2022

Viewed by 1903

Abstract

Phage display technology has been a powerful tool in peptide drug development. However, the supremacy of phage display-based peptide drug discovery is plagued by the follow-up process of peptides synthesis, which is costly and time consuming, but is necessary for the accurate measurement [...] Read more.

Phage display technology has been a powerful tool in peptide drug development. However, the supremacy of phage display-based peptide drug discovery is plagued by the follow-up process of peptides synthesis, which is costly and time consuming, but is necessary for the accurate measurement of binding kinetics in order to properly triage the best peptide leads during the affinity maturation stages. A sensitive technology is needed for directly measuring the binding kinetics of peptides on phages to reduce the time and cost of the entire process. Here, we show the capability of a charge-sensitive optical detection (CSOD) method for the direct quantification of binding kinetics of phage-displayed peptides to their target protein, using whole phages. We anticipate CSOD will contribute to streamline the process of phage display-based drug discovery. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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Figure 1
Schematic of charge-sensitive optical detection of binding kinetics between M13 phage-displayed peptides and the protein target. An optical fiber is inserted into a glass capillary and the fiber tip is dipped into a microplate well between a pair of steel electrodes. An alternating electric field is applied through the electrodes to drive the fiber tip into oscillation. The light coming out from the tip bottom is collected by a 40× objective and measured by a quadrant cell detector. For the binding kinetics measurement, the M13 phages with peptides displayed on pVIII coating proteins are immobilized on the fiber tip, and the tip is inserted into a well with target protein. Upon binding, the net charges of the M13 phages are changed and the oscillation amplitude of the fiber tip changes as well. By recording the oscillation change in real-time, the binding kinetics between the peptide, and the protein can be quantified. Full article ">Figure 2
CSOD data processing workflow. (a) Schematic shows the light out of the fiber tip projected on the center of the quadrant cell detector, where the sensor response is calculated with the equation shown on the right. Q1 to Q4 are the signals collected by the quadrant cell detector. (b) Representative measured detector response plotted against time with a sampling rate of 16.000 data points per second. (c) The calibration curve and linear region of the quadrant cell detector. (d) The calibrated fiber oscillation amplitudes over time. (e) The fast Fourier transform (FFT) result of the fiber oscillation amplitude in 1 s, where the peak at 511 Hz clearly shows the fiber vibrates at the set frequency. Full article ">Figure 3
CSOD measurement results of PCSK9 binding to different peptides displayed on the M13 phage surface. Sample IDs are marked on the top right corner of each plot and the details of the samples are listed in <a href="#biosensors-12-00394-t002" class="html-table">Table 2</a>. (a) Binding curves for different peptides. The fiber probes were switched from a well containing a buffer to a well containing PCSK9 at 0 s for the measurement of the association process (red arrow) and then switched back to the buffer well at the time indicated by the black arrow for the measurement of the dissociation process. (b) CSOD measurement results of PCSK9 binding to negative samples. The red arrows indicate switching the fiber probe from the buffer well to a well with 1000 nM PCSK9 solution. Full article ">Figure 4
SPR measurement results of PCSK9 binding to synthesized pep2-8. The synthesized peptide was immobilized to a streptavidin-coated gold surface. Different concentrations of PCSK9 were flowed to the surface to measure the binding kinetics. By fitting the data obtained with different concentrations, the average and standard deviation for ka, kd, and KD were determined to be (3.88 ± 3.26) × 105 M−1s−1, (1.73 ± 0.25) × 10−1 s−1, and 0.985 ± 0.724 µM, respectively. Full article ">

15 pages, 2811 KiB

Open AccessArticle

Single-Mode Input Fiber Combined with Multimode Sensing Fiber Used in Brillouin Optical Time-Domain Reflectometry

by Yongqian Li, Haijun Fan, Lixin Zhang, Zijuan Liu, Lei Wang, Jiaqi Wu and Shaokang Wang

Photonics 2022, 9(6), 398; https://doi.org/10.3390/photonics9060398 - 5 Jun 2022

Cited by 3 | Viewed by 2100

Abstract

Conventional single-mode fiber (SMF) Brillouin optical time-domain reflectometry (BOTDR) suffers from a low signal-to-noise ratio (SNR) and severe sensing reliability due to the influence of the stimulated Brillouin scattering threshold and bend loss. In this study, a simple and low-cost distributed sensing structure, [...] Read more.

Conventional single-mode fiber (SMF) Brillouin optical time-domain reflectometry (BOTDR) suffers from a low signal-to-noise ratio (SNR) and severe sensing reliability due to the influence of the stimulated Brillouin scattering threshold and bend loss. In this study, a simple and low-cost distributed sensing structure, with a single-mode input fiber alignment fusion and a 50 μm diameter graded index multimode sensing fiber, is designed, and the SNR characteristic is investigated. Through theoretical derivation and experimental verification, a higher SNR and excellent bending resistance are realized in BOTDR. The experimentally measured improvements in the SNR of the proposed sensing structure over the SMF at the beginning and end of a 5 km fiber are 2.5 dB and 1.3 dB, respectively. The minimum bending radius of the sensing structure is 2.25 mm, which is much better than that of the SMFs. The bidirectional optical losses between the SMF and the 50 μm graded index multimode fiber are measured by a simple experiment system and are 0.106 dB and 1.35 dB, respectively. The temperature-sensing characteristics of the sensing structure are measured by the self-built frequency-shift local heterodyne BOTDR sensor, and the measured temperature sensitivity and accuracy are 0.946 MHz/℃ and 1 ℃, respectively. The design provides a reference for BOTDR with a high SNR and has great potential for structural safety and health monitoring of infrastructures. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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19 pages, 5376 KiB

Open AccessArticle

Sensitivity Improvement of Multi-Slot Subwavelength Bragg Grating Refractive Index Sensors by Increasing the Waveguide Height or Suspending the Sensor

by Siim Heinsalu and Katsuyuki Utaka

Sensors 2022, 22(11), 4136; https://doi.org/10.3390/s22114136 - 29 May 2022

Viewed by 2300

Abstract

We present two methods of improving wavelength sensitivity for multi-slot sub-wavelength Bragg grating (MS-SW BG) refractive index sensors. The sensor structure is designed to have high optical mode confinement in the gaps between the silicon pillars whereby the surrounding medium interaction is high, [...] Read more.

We present two methods of improving wavelength sensitivity for multi-slot sub-wavelength Bragg grating (MS-SW BG) refractive index sensors. The sensor structure is designed to have high optical mode confinement in the gaps between the silicon pillars whereby the surrounding medium interaction is high, thus improving the sensitivity. Further sensitivity improvements are achieved by increasing the waveguide height or suspending the sensor. The second option, sensor suspension, additionally requires supporting modifications in which case various configurations are considered. After the optimization of the parameters the sensors were fabricated. For the case of a waveguide height increase to 500 nm, the sensitivity of 850 nm/RIU was obtained; for sensor suspension with fully etched holes, 922 nm/RIU; for the case of not fully etched holes, 1100 nm/RIU; with the sensor lengths of about 10 µm for all cases. These values show improvements by 16.5%, 25%, and 50.5%, respectively, compared to the previous result where the height was fixed to 340 nm. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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17 pages, 14192 KiB

Open AccessArticle

High Sensitivity Surface Plasmon Resonance Sensor Based on a Ge-Doped Defect and D-Shaped Microstructured Optical Fiber

by Nilson H. O. Cunha and José P. Da Silva

Sensors 2022, 22(9), 3220; https://doi.org/10.3390/s22093220 - 22 Apr 2022

Cited by 10 | Viewed by 2316

Abstract

In this work a plasmonic sensor with a D-Shaped microstructured optical fiber

(MOF)

is proposed to detect a wide range of analyte refractive index

(RI; n_{a})

by doping the pure silica

({SiO}_{2})

core [...] Read more.

In this work a plasmonic sensor with a D-Shaped microstructured optical fiber

(MOF)

is proposed to detect a wide range of analyte refractive index

(RI; n_{a})

by doping the pure silica

({SiO}_{2})

core with distinct concentrations of Germanium Dioxide

({GeO}_{2})

, causing the presentation of high spectral sensitivity. In this case, the fiber is shaped by polishing a coating of

{SiO}_{2}

, on the region that will be doped with

{GeO}_{2}

, in the polished area, a thin gold

(Au)

layer, which constitutes the plasmonic material, is introduced, followed by the analyte, in a way which the gold layer is deposited between the

{SiO}_{2}

. and the analyte. The numerical results obtained in the study shows that the sensor can determine efficiently a range of 0.13 refractive index units

(RIU)

, with a limit operation where

n_{a}

varies from 1.32 to 1.45. Within this application, the sensor has reached an average wavelength sensitivity

(WS)

of up to

11, 650.63 nm / RIU

. With this level of sensitivity, the D-Shaped format and wide range of

n_{a}

detection, the proposed fiber has great potential for sensing applications in several areas. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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11 pages, 2970 KiB

Open AccessCommunication

Sapphire Photonic Crystal Waveguides with Integrated Bragg Grating Structure

by Stefan Kefer, Gian-Luca Roth, Julian Zettl, Bernhard Schmauss and Ralf Hellmann

Photonics 2022, 9(4), 234; https://doi.org/10.3390/photonics9040234 - 1 Apr 2022

Cited by 7 | Viewed by 2755

Abstract

This contribution demonstrates photonic crystal waveguides generated within bulk planar sapphire substrates. A femtosecond laser is used to modify the refractive index in a hexagonal pattern around the pristine waveguide core. Near-field measurements reveal single-mode behavior at a wavelength of 1550 nm and [...] Read more.

This contribution demonstrates photonic crystal waveguides generated within bulk planar sapphire substrates. A femtosecond laser is used to modify the refractive index in a hexagonal pattern around the pristine waveguide core. Near-field measurements reveal single-mode behavior at a wavelength of 1550 nm and the possibility to adapt the mode-field diameter. Based on far-field examinations, the effective refractive index contrast between the pristine waveguide core and depressed cladding is estimated to 3·10⁻⁴. Additionally, Bragg gratings are generated within the waveguide core. Due to the inherent birefringence of Al₂O₃, the gratings exhibit two distinct wavelengths of main reflection. Each reflection peak exhibits a narrow spectral full width at a half maximum of 130 pm and can be selectively addressed by exciting the birefringent waveguide with appropriately polarized light. Furthermore, a waveguide attenuation of 1 dB cm⁻¹ is determined. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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Figure 1
Illustration of the sapphire crystal structure. A,C,N and R indicate the respective crystal planes. Full article ">Figure 2
(a) Schematic of the employed femtosecond laser setup. (b) Exemplary cross-sectional schematic of a sapphire photonic crystal waveguide (S-PCWG) with integrated Bragg grating (BG). dx indicates the distance of two modification lines in x-direction, while Dx and Dy represent the theoretical inner hexagon diameters in x- and y-direction, respectively. Full article ">Figure 3
Bright-field microscopy images of a sapphire photonic crystal waveguide with 5 µm modification distance: (a) top view; (b) cross-section. Full article ">Figure 4
(a) Exemplary near-field image of an S-PCWG with a modification distance of 7 µm. (b) Intensity distribution along the x-axis cross-section for waveguides with modification distances of 7 and 9 µm. (c) Intensity distribution along the y-axis cross-section. (d) Mode-field diameter as a function of the modification distance. The respective core diameters in x- and y-direction are also indicated. Full article ">Figure 5
(a) Far-field image at a relative distance change Δz of 0 mm. (b) Far-field image at a relative dis-tance change Δz of 10 mm. (c) Respective far-field diameters in x- and y-direction as a function of the relative distance change. Full article ">Figure 6
(a) Schematic of the employed evaluation setup for S-PCWGs with integrated Bragg grating structures. (b) Exemplary Bragg reflection signal when an S-PCWG with a modification distance of 5 µm is excited with linearly polarized light, oriented in parallel or perpendicular to the sapphire crystal’s C-axis, as well as unpolarized radiation. Full article ">Figure 7
(a) Schematic of Bragg grating positions within the S-PCWG. (b) Bragg reflection signal of both coupling directions. (c) Forward and backward coupling peak power ratio as a function of Bragg grating distance. Full article ">

16 pages, 4764 KiB

Open AccessArticle

Distorted Acquisition of Dynamic Events Sensed by Frequency-Scanning Fiber-Optic Interrogators and a Mitigation Strategy

by Hari Datta Bhatta, Roy Davidi, Arie Yeredor and Moshe Tur

Sensors 2022, 22(6), 2403; https://doi.org/10.3390/s22062403 - 21 Mar 2022

Cited by 2 | Viewed by 2045

Abstract

Fiber-optic dynamic interrogators, which use periodic frequency scanning, actually sample a time-varying measurand on a non-uniform time grid. Commonly, however, the sampled values are reported on a uniform time grid, synchronized with the periodic scanning. It is the novel and noteworthy message of [...] Read more.

Fiber-optic dynamic interrogators, which use periodic frequency scanning, actually sample a time-varying measurand on a non-uniform time grid. Commonly, however, the sampled values are reported on a uniform time grid, synchronized with the periodic scanning. It is the novel and noteworthy message of this paper that this artificial assignment may give rise to significant distortions in the recovered signal. These distortions increase with both the signal frequency and measurand dynamic range for a given sampling rate and frequency scanning span of the interrogator. They may reach disturbing values in dynamic interrogators, which trade-off scanning speed with scanning span. The paper also calls for manufacturers of such interrogators to report the sampled values along with their instants of acquisition, allowing interpolation algorithms to substantially reduce the distortion. Experimental verification of a simulative analysis includes: (i) a commercial dynamic interrogator of ‘continuous’ FBG fibers that attributes the measurand values to a uniform time grid; as well as (ii) a dynamic Brillouin Optical time Domain (BOTDA) laboratory setup, which provides the sampled measurand values together with the sampling instants. Here, using the available measurand-dependent sampling instants, we demonstrate a significantly cleaner signal recovery using spline interpolation. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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17 pages, 10725 KiB

Open AccessReview

Recent Advances in Surface Plasmon Resonance Sensors for Sensitive Optical Detection of Pathogens

by Joon-Ha Park, Yeon-Woo Cho and Tae-Hyung Kim

Biosensors 2022, 12(3), 180; https://doi.org/10.3390/bios12030180 - 17 Mar 2022

Cited by 54 | Viewed by 6409

Abstract

The advancement of science and technology has led to the recent development of highly sensitive pathogen biosensing techniques. The effective treatment of pathogen infections requires sensing technologies to not only be sensitive but also render results in real-time. This review thus summarises the [...] Read more.

The advancement of science and technology has led to the recent development of highly sensitive pathogen biosensing techniques. The effective treatment of pathogen infections requires sensing technologies to not only be sensitive but also render results in real-time. This review thus summarises the recent advances in optical surface plasmon resonance (SPR) sensor technology, which possesses the aforementioned advantages. Specifically, this technology allows for the detection of specific pathogens by applying nano-sized materials. This review focuses on various nanomaterials that are used to ensure the performance and high selectivity of SPR sensors. This review will undoubtedly accelerate the development of optical biosensing technology, thus allowing for real-time diagnosis and the timely delivery of appropriate treatments as well as preventing the spread of highly contagious pathogens. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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Figure 1
Schematic of recent advances in SPR sensor technology with various nanomaterials and applications for pathogen detection. Full article ">Figure 2
(a) SPR signal intensity vs. incident angle plot with polyuria (left) and oliguria (right). (b) Variation in parameters for different sensing medium refractive indices in pure water, polyuria, and oliguria. With permission from [<a href="#B76-biosensors-12-00180" class="html-bibr">76</a>], Copyright 2020, Springer. Full article ">Figure 3
(a) Schematic illustration of the fabricated gold nanospike-based SPR sensor. (b) Plot representing the detection limit for the analyte. (c) Selective affinity test against other interference substances. With permission from [<a href="#B81-biosensors-12-00180" class="html-bibr">81</a>], Copyright 2020, ELSEVIER. Full article ">Figure 4
(a) Schematic illustration of the biosensor fabrication process. (b) Plot indicating the limit of detection and linear range. (c) Selectivity of the fabricated platform. With permission from [<a href="#B83-biosensors-12-00180" class="html-bibr">83</a>], Copyright 2019, MDPI. Full article ">Figure 5
(a) Schematic illustration of SPR sensor fabrication via the sandwich aptamer technique. (b) Linear plot of norovirus spike protein-sensing performance. (c) Linear plot of norovirus spike protein-sensing performance without gold nanorods. With permission from [<a href="#B88-biosensors-12-00180" class="html-bibr">88</a>], Copyright 2018, American Chemical Society. Full article ">Figure 6
(a) Schematic illustration of an experimental setup to test sensors. (b) Field emission scanning electron microscope (FESEM) image of the fabricated optic fibre surface. (c) Transmission spectra plot indicating the limit of detection. (d) Atomic force microscope image analysis of the fabricated optic fibre surface. With permission from [<a href="#B91-biosensors-12-00180" class="html-bibr">91</a>], Copyright 2018, Elsevier. Full article ">

14 pages, 6093 KiB

Open AccessArticle

Silicone Rubber Fabry-Perot Pressure Sensor Based on a Spherical Optical Fiber End Face

by Changxing Jiang, Xiaohua Lei, Yuru Chen, Shaojie Lv, Xianming Liu and Peng Zhang

Sensors 2022, 22(5), 1862; https://doi.org/10.3390/s22051862 - 26 Feb 2022

Cited by 3 | Viewed by 2456

Abstract

To improve the fringe contrast and the sensitivity of Fabry-Perot (FP) pressure sensors, a silicone rubber FP pressure sensor based on a spherical optical fiber end face is proposed. The ratio of silicone rubber ingredients and the diameter and thickness of silicone rubber [...] Read more.

To improve the fringe contrast and the sensitivity of Fabry-Perot (FP) pressure sensors, a silicone rubber FP pressure sensor based on a spherical optical fiber end face is proposed. The ratio of silicone rubber ingredients and the diameter and thickness of silicone rubber diaphragm were optimized by a simulation based on experimental tests that analyzed elastic parameters, and the influence of the radius of a spherical optical fiber and the initial cavity length of the sensor on the fringe contrast was investigated and optimized. Pressure sensor samples were fabricated for pressure test and temperature cross-influence test. Gas pressure experimental results within a pressure range of 0~40 kPa show the average sensitivity of the sensor is −154.56 nm/kPa and repeatability error is less than 0.71%. Long-term pressure experimental results show it has good repeatability and stability. Temperature experimental results show its temperature cross-sensitivity is 0.143 kPa/°C. The good performance of the proposed FP pressure sensor will expand its applications in biochemical applications, especially in human body pressure monitoring. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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21 pages, 4539 KiB

Open AccessArticle

Fibre Bragg Grating Based Interface Pressure Sensor for Compression Therapy

by James A. Bradbury, Qimei Zhang, Francisco U. Hernandez Ledezma, Ricardo Correia, Serhiy Korposh, Barrie R. Hayes-Gill, Ferdinand Tamoué, Alison Parnham, Simon A. McMaster and Stephen P. Morgan

Sensors 2022, 22(5), 1798; https://doi.org/10.3390/s22051798 - 24 Feb 2022

Cited by 4 | Viewed by 3123

Abstract

Compression therapy is widely used as the gold standard for management of chronic venous insufficiency and venous leg ulcers, and the amount of pressure applied during the compression therapy is crucial in supporting healing. A fibre optic pressure sensor using Fibre Bragg Gratings [...] Read more.

Compression therapy is widely used as the gold standard for management of chronic venous insufficiency and venous leg ulcers, and the amount of pressure applied during the compression therapy is crucial in supporting healing. A fibre optic pressure sensor using Fibre Bragg Gratings (FBGs) is developed in this paper to measure sub-bandage pressure whilst removing cross-sensitivity due to strain in the fibre and temperature. The interface pressure is measured by an FBG encapsulated in a polymer and housed in a textile to minimise discomfort for the patient. The repeatability of a manual fabrication process is investigated by fabricating and calibrating ten sensors. A customized calibration setup consisting of a programmable translation stage and a weighing scale gives sensitivities in the range 0.4–1.5 pm/mmHg (2.6–11.3 pm/kPa). An alternative calibration method using a rigid plastic cylinder and a blood pressure cuff is also demonstrated. Investigations are performed with the sensor under a compression bandage on a phantom leg to test the response of the sensor to changing pressures in static situations. Measurements are taken on a human subject to demonstrate changes in interface pressure under a compression bandage during motion to mimic a clinical application. These results are compared to the current gold standard medical sensor using a Bland–Altman analysis, with a median bias ranging from −4.6 to −20.4 mmHg, upper limit of agreement (LOA) from −13.5 to 2.7 mmHg and lower LOA from −32.4 to −7.7 mmHg. The sensor has the potential to be used as a training tool for nurses and can be left in situ to monitor bandage pressure during compression therapy. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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27 pages, 6428 KiB

Open AccessArticle

Residual Interpolation Integrated Pixel-by-Pixel Adaptive Iterative Process for Division of Focal Plane Polarimeters

by Jie Yang, Weiqi Jin, Su Qiu, Fuduo Xue and Meishu Wang

Sensors 2022, 22(4), 1529; https://doi.org/10.3390/s22041529 - 16 Feb 2022

Cited by 5 | Viewed by 2050

Abstract

Residual interpolations are effective methods to reduce the instantaneous field-of-view error of division of focal plane (DoFP) polarimeters. However, their guide-image selection strategies are improper, and do not consider the DoFP polarimeters’ spatial sampling modes. Thus, we propose a residual interpolation method with [...] Read more.

Residual interpolations are effective methods to reduce the instantaneous field-of-view error of division of focal plane (DoFP) polarimeters. However, their guide-image selection strategies are improper, and do not consider the DoFP polarimeters’ spatial sampling modes. Thus, we propose a residual interpolation method with a new guide-image selection strategy based on the spatial layout of the pixeled polarizer array to improve the sampling rate of the guide image. The interpolation performance is also improved by the proposed pixel-by-pixel, adaptive iterative process and the weighted average fusion of the results of the minimized residual and minimized Laplacian energy guide filters. Visual and objective evaluations demonstrate the proposed method’s superiority to the existing state-of-the-art methods. The proposed method proves that considering the spatial layout of the pixeled polarizer array on the physical level is vital to improving the performance of interpolation methods for DoFP polarimeters. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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11 pages, 4047 KiB

Open AccessArticle

Simultaneous Sensitive Determination of δ¹³C, δ¹⁸O, and δ¹⁷O in Human Breath CO₂ Based on ICL Direct Absorption Spectroscopy

by Ligang Shao, Jiaoxu Mei, Jiajin Chen, Tu Tan, Guishi Wang, Kun Liu and Xiaoming Gao

Sensors 2022, 22(4), 1527; https://doi.org/10.3390/s22041527 - 16 Feb 2022

Cited by 4 | Viewed by 2102

Abstract

Previous research revealed that isotopes ¹³C and ¹⁸O of exhaled CO₂ have the potential link with Helicobacter pylori; however, the ¹⁷O isotope has received very little attention. We developed a sensitive spectroscopic sensor for simultaneous δ¹³C, [...] Read more.

Previous research revealed that isotopes ¹³C and ¹⁸O of exhaled CO₂ have the potential link with Helicobacter pylori; however, the ¹⁷O isotope has received very little attention. We developed a sensitive spectroscopic sensor for simultaneous δ¹³C, δ¹⁸O, and δ¹⁷O analysis of human breath CO₂ based on mid-infrared laser direct absorption spectroscopy with an interband cascade laser (ICL) at 4.33 μm. There was a gas cell with a small volume of less than 5 mL, and the pressure in the gas cell was precisely controlled with a standard deviation of 0.0035 Torr. Moreover, real-time breath sampling and batch operation were achieved in gas inlets. The theoretical drifts for δ¹³C, δ¹⁸O, and δ¹⁷O measurement caused by temperature were minimized to 0.017‰, 0.024‰, and 0.021‰, respectively, thanks to the precise temperature control with a standard deviation of 0.0013 °C. After absolute temperature correction, the error between the system responded δ-value and the reference is less than 0.3‰. According to Allan variance analysis, the system precisions for δ¹³C, δ¹⁸O, and δ¹⁷O were 0.12‰, 0.18‰, and 0.47‰, respectively, at 1 s integration time, which were close to the real-time measurement errors of six repeated exhalations. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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10 pages, 1298 KiB

Open AccessCommunication

Single-Layer-Graphene-Coated and Gold-Film-Based Surface Plasmon Resonance Prism Coupler Sensor for Immunoglobulin G Detection

by Zhe-Wei Yang, Thi-Thu-Hien Pham, Chin-Chi Hsu, Chi-Hsiang Lien and Quoc-Hung Phan

Sensors 2022, 22(4), 1362; https://doi.org/10.3390/s22041362 - 10 Feb 2022

Cited by 14 | Viewed by 2798

Abstract

A graphene-based surface plasmon resonance (SPR) prism coupler sensor is proposed for the rapid detection of immunoglobulin G (IgG) antibodies. The feasibility of the proposed sensor is demonstrated by measuring the IgG concentration in phantom mouse and human serum solutions over the range [...] Read more.

A graphene-based surface plasmon resonance (SPR) prism coupler sensor is proposed for the rapid detection of immunoglobulin G (IgG) antibodies. The feasibility of the proposed sensor is demonstrated by measuring the IgG concentration in phantom mouse and human serum solutions over the range of 0–250 ng/mL. The results show that the circular dichroism and principal fast axis angle of linear birefringence increase in line with increases in IgG concentration over the considered range. Moreover, the proposed device has a resolution of 5–10 ng/mL and a response time of less than three minutes. In general, the sensor provides a promising approach for IgG detection and has significant potential for rapid infectious viral disease testing applications. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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12 pages, 4490 KiB

Open AccessArticle

Fluorescent “OFF–ON” Sensors for the Detection of Sn²⁺ Ions Based on Amine-Functionalized Rhodamine 6G

by Balamurugan Rathinam, Vajjiravel Murugesan and Bo-Tau Liu

Chemosensors 2022, 10(2), 69; https://doi.org/10.3390/chemosensors10020069 - 9 Feb 2022

Cited by 14 | Viewed by 3063

Abstract

These structurally isomeric rhodamine 6G-based amino derivatives are designed to detect Sn²⁺ ions. The receptors exhibit rapid fluorescent “turn-on” responses towards Sn²⁺. The absorption (530 nm) and fluorescent intensity (551 nm) of the receptors increase when increasing the concentration of [...] Read more.

These structurally isomeric rhodamine 6G-based amino derivatives are designed to detect Sn²⁺ ions. The receptors exhibit rapid fluorescent “turn-on” responses towards Sn²⁺. The absorption (530 nm) and fluorescent intensity (551 nm) of the receptors increase when increasing the concentration of Sn²⁺. The hydrazine derivative exhibits more rapid sensitivity towards Sn²⁺ than the ethylene diamine derivative, indicating that the presence of an alkyl chain in the diamine decreases the sensitivity of the receptors towards Sn²⁺. The presence of carbonyl groups and terminal amino groups strongly influences the sensitivity of the chemosensors toward Sn²⁺ by a spirolactam ring-opening mechanism. The receptors exhibit 1:1 complexation with Sn²⁺ as evidenced by Job plot, and the corresponding limit of detection was found to be 1.62 × 10⁻⁷ M. The fluorescence images of the receptors and their complexes reveal their potential applications for imaging of Sn²⁺ in real/online samples. Full article

(This article belongs to the Topic Advances in Optical Sensors)

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