Photonics

8 pages, 2473 KiB

Open AccessArticle

Image Encryption System Based on a Nonlinear Joint Transform Correlator for the Simultaneous Authentication of Two Users

by Juan M. Vilardy O., María S. Millán and Elisabet Pérez-Cabré

Photonics 2019, 6(4), 128; https://doi.org/10.3390/photonics6040128 - 14 Dec 2019

Cited by 5 | Viewed by 2779

Abstract

We propose a new encryption system based on a nonlinear joint transform correlator (JTC) using the information of two biometrics (one digital fingerprint for each user) as security keys of the encryption system. In order to perform the decryption and authentication in a [...] Read more.

We propose a new encryption system based on a nonlinear joint transform correlator (JTC) using the information of two biometrics (one digital fingerprint for each user) as security keys of the encryption system. In order to perform the decryption and authentication in a proper way, it is necessary to have the two digital fingerprints from the respective users whose simultaneous authentication is pursued. The proposed security system is developed in the Fourier domain. The nonlinearity of the JTC along with the five security keys given by the three random phase masks and the two digital fingerprints of the two users allow an increase of the system security against brute force and plaintext attacks. The feasibility and validity of this proposal is demonstrated using digital fingerprints as biometrics in numerical experiments. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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10 pages, 5481 KiB

Open AccessArticle

The Effect of Thickness on the Properties of Laser-Deposited NiBSi-WC Coating on a Cu-Cr-Zr Substrate

by Yury Korobov, Yulia Khudorozhkova, Holger Hillig, Alexander Vopneruk, Aleksandr Kotelnikov, Sergey Burov, Prabu Balu, Alexey Makarov and Alexey Chernov

Photonics 2019, 6(4), 127; https://doi.org/10.3390/photonics6040127 - 13 Dec 2019

Cited by 3 | Viewed by 3145

Abstract

Ni/60WC coatings on copper substrate were placed via laser deposition (LD). A structural study was conducted using electron microscopy and a microhardness evaluation. Two body abrasive wear tests were conducted with a pin-on-plate reciprocating technique. A tool steel X12MF GOST 5960 (C-Cr-Mo-V 1.6-12-0.5-0.2) [...] Read more.

Ni/60WC coatings on copper substrate were placed via laser deposition (LD). A structural study was conducted using electron microscopy and a microhardness evaluation. Two body abrasive wear tests were conducted with a pin-on-plate reciprocating technique. A tool steel X12MF GOST 5960 (C-Cr-Mo-V 1.6-12-0.5-0.2) with a hardness of 63 HRC was used as a counterpart. The following results were obtained: Precipitation of the secondary carbides takes place in the thicker layers. Their hardness is lower than that of the primary carbides in the deposition (2425 HV vs. 2757 HV) because they mix with the matrix material. In the thin layers, precipitation is restricted due to a higher cooling rate. For both LD coatings, the carbide’s hardness increases compared to the initial mono-tungsten carbide (WC)-containing powder (2756 HV vs. 2200 HV). Such a high level of microhardness reflects the combined influence of a low level of thermal destruction of carbides during laser deposition and the formation of a boride-strengthening phase from the matrix powder. The thicker layer showed a higher wear resistance; weight loss was 20% lower. The changes in the thickness of the laser deposited Ni-WC coating altered its structure and wear resistance. Full article

(This article belongs to the Special Issue Advanced Optical Materials and Devices)

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View of the samples as deposited: (a) Laser deposition (LD)-thin; (b) LD-thick. Full article ">Figure 2
SEM image: Carbide particles surrounded by a matrix in LD coating: (a) LD-thin; (b) LD-thick. Full article ">Figure 3
Elemental mapping analysis in the characteristic spectra: (a) Ni; (b) W; (c) B. The image corresponds to LD-thin coating, <a href="#photonics-06-00127-f002" class="html-fig">Figure 2</a>a. Full article ">Figure 4
Elemental mapping analysis in the characteristic spectra: (a) Ni; (b) W; (c) B. The image corresponds to LD-thick coating, <a href="#photonics-06-00127-f002" class="html-fig">Figure 2</a>b. Full article ">Figure 5
A view of crack propagation in carbide particle of LD-thick layer. Full article ">Figure 6
The distribution of elements in the cross section of the coating from the surface to the substrate, (a) LD-thin; (b) LD-thick. Full article ">Figure 7
Wear surface: (a) Thick coating; (b) thin coating. (1) Matrix; (2) supporting sections of carbides; (3) transitional section. Full article ">

13 pages, 12141 KiB

Open AccessArticle

An Optoelectronic Targeting System for Measuring the Distribution of Projectile Motion Based on the Subdivision of a Light Screen

by Wenbo Chu, Bin Zhang, Baowei Liu, Zhiguo Gui and Donge Zhao

Photonics 2019, 6(4), 126; https://doi.org/10.3390/photonics6040126 - 12 Dec 2019

Cited by 12 | Viewed by 2812

Abstract

This paper proposes a cost-effective, compact, noncontacting optoelectronic targeting system for measuring the distribution of projectile motion. The major elements of this system include a light emitting diode (LED) array, photodiode detecting array, double-layered aperture arrays, adaptive threshold circuit, and date acquisition. Through [...] Read more.

This paper proposes a cost-effective, compact, noncontacting optoelectronic targeting system for measuring the distribution of projectile motion. The major elements of this system include a light emitting diode (LED) array, photodiode detecting array, double-layered aperture arrays, adaptive threshold circuit, and date acquisition. Through cooperating with double-layered aperture arrays, the system effectively reduces the radiation width of the light source to the photodiode detecting surface, and filters out the influence of incident light from the adjacent apertures on both sides above each photodiode to the corresponding photodiode detecting surface. It realizes that the response of the photodiode array corresponds to the coordinates of the light screen one by one. Through the sensitivity analysis of the light screen of the system, the system detecting threshold when the projectile passes through the light screen is calculated, and the corresponding adaptive threshold circuit is designed to prevent misjudgment when the system works. The measuring error of the system can reach ±2 mm by experimental verification. Compared with other projectile’s distribution measuring systems, the proposed system has the advantages of having high precision, convenient debugging, is nondestructive, and is a noncontact system. Full article

(This article belongs to the Section Lasers, Light Sources and Sensors)

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14 pages, 791 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Synchronization of Mutually Delay-Coupled Quantum Cascade Lasers with Distinct Pump Strengths

by Thomas Erneux and Daan Lenstra

Photonics 2019, 6(4), 125; https://doi.org/10.3390/photonics6040125 - 10 Dec 2019

Cited by 14 | Viewed by 2966

Abstract

The rate equations for two delay-coupled quantum cascade lasers are investigated analytically in the limit of weak coupling and small frequency detuning. We mathematically derive two coupled Adler delay differential equations for the phases of the two electrical fields and show that these [...] Read more.

The rate equations for two delay-coupled quantum cascade lasers are investigated analytically in the limit of weak coupling and small frequency detuning. We mathematically derive two coupled Adler delay differential equations for the phases of the two electrical fields and show that these equations are no longer valid if the ratio of the two pump parameters is below a critical power of the coupling constant. We analyze this particular case and derive new equations for a single optically injected laser where the delay is no longer present in the arguments of the dependent variables. Our analysis is motivated by the observations of Bogris et al. (IEEE J. Sel. Top. Quant. El. 23, 1500107 (2017)), who found better sensing performance using two coupled quantum cascade lasers when one laser was operating close to the threshold. Full article

(This article belongs to the Special Issue Semiconductor Laser Dynamics: Fundamentals and Applications)

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11 pages, 943 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Task-Independent Computational Abilities of Semiconductor Lasers with Delayed Optical Feedback for Reservoir Computing

by Krishan Harkhoe and Guy Van der Sande

Photonics 2019, 6(4), 124; https://doi.org/10.3390/photonics6040124 - 2 Dec 2019

Cited by 25 | Viewed by 3988

Abstract

Reservoir computing has rekindled neuromorphic computing in photonics. One of the simplest technological implementations of reservoir computing consists of a semiconductor laser with delayed optical feedback. In this delay-based scheme, virtual nodes are distributed in time with a certain node distance and form [...] Read more.

Reservoir computing has rekindled neuromorphic computing in photonics. One of the simplest technological implementations of reservoir computing consists of a semiconductor laser with delayed optical feedback. In this delay-based scheme, virtual nodes are distributed in time with a certain node distance and form a time-multiplexed network. The information processing performance of a semiconductor laser-based reservoir computing (RC) system is usually analysed by way of testing the laser-based reservoir computer on specific benchmark tasks. In this work, we will illustrate the optimal performance of the system on a chaotic time-series prediction benchmark. However, the goal is to analyse the reservoir’s performance in a task-independent way. This is done by calculating the computational capacity, a measure for the total number of independent calculations that the system can handle. We focus on the dependence of the computational capacity on the specifics of the masking procedure. We find that the computational capacity depends strongly on the virtual node distance with an optimal node spacing of 30 ps. In addition, we show that the computational capacity can be further increased by allowing for a well chosen mismatch between delay and input data sample time. Full article

(This article belongs to the Special Issue Semiconductor Laser Dynamics: Fundamentals and Applications)

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18 pages, 3144 KiB

Open AccessArticle

A Study into the Effects of Factors Influencing an Underwater, Single-Pixel Imaging System’s Performance

by Qi Chen, Anumol Mathai, Xiping Xu and Xin Wang

Photonics 2019, 6(4), 123; https://doi.org/10.3390/photonics6040123 - 27 Nov 2019

Cited by 18 | Viewed by 3603

Abstract

Underwater detection has always been a challenge due to the limitations caused by scattering and absorption in the underwater environment. Because of their great penetration abilities, lasers have become the most suitable technology for underwater detection. In all underwater laser applications, the reflected [...] Read more.

Underwater detection has always been a challenge due to the limitations caused by scattering and absorption in the underwater environment. Because of their great penetration abilities, lasers have become the most suitable technology for underwater detection. In all underwater laser applications, the reflected laser pulse which contains the key information for most of the system is highly degraded along the laser’s propagation path and during reflection. This has a direct impact on the system’s performance, especially for single-pixel imaging (SPI) which is very dependent on light-intensity information. Due to the complications in the underwater environment, it is necessary to study the influential factors and their impacts on underwater SPI. In this study, we investigated the influence of the angle of incidence, target distance, and medium attenuation. A systematic investigation of the influential factors on the reflectance and ranging accuracy was performed theoretically and experimentally. The theoretical analysis was demonstrated based on the bidirectional reflection distribution function (BRDF) and laser detection and ranging (LADAR) model. Moreover, 2D single-pixel imaging (SPI) systems were setup for experimental investigation. The experimental results agree well with the theoretical results, which show the system’s dependency on the reflection intensity caused by the angle of incidence, target distance, and medium attenuation. The findings should be a reference for works looking to improve the performance of an underwater SPI system. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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9 pages, 1965 KiB

Open AccessArticle

Parity–Time Symmetry in Bidirectionally Coupled Semiconductor Lasers

by Andrew Wilkey, Joseph Suelzer, Yogesh Joglekar and Gautam Vemuri

Photonics 2019, 6(4), 122; https://doi.org/10.3390/photonics6040122 - 27 Nov 2019

Cited by 9 | Viewed by 3327

Abstract

We report on the numerical analysis of intensity dynamics of a pair of mutually coupled, single-mode semiconductor lasers that are operated in a configuration that leads to features reminiscent of parity–time symmetry. Starting from the rate equations for the intracavity electric fields of [...] Read more.

We report on the numerical analysis of intensity dynamics of a pair of mutually coupled, single-mode semiconductor lasers that are operated in a configuration that leads to features reminiscent of parity–time symmetry. Starting from the rate equations for the intracavity electric fields of the two lasers and the rate equations for carrier inversions, we show how these equations reduce to a simple 2 × 2 effective Hamiltonian that is identical to that of a typical parity–time (PT)-symmetric dimer. After establishing that a pair of coupled semiconductor lasers could be PT-symmetric, we solve the full set of rate equations and show that despite complicating factors like gain saturation and nonlinearities, the rate equation model predicts intensity dynamics that are akin to those in a PT-symmetric system. The article describes some of the advantages of using semiconductor lasers to realize a PT-symmetric system and concludes with some possible directions for future work on this system. Full article

(This article belongs to the Special Issue Semiconductor Laser Dynamics: Fundamentals and Applications)

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9 pages, 1740 KiB

Open AccessArticle

Image Encryption and Decryption Systems Using the Jigsaw Transform and the Iterative Finite Field Cosine Transform

by Juan M. Vilardy O., Leiner Barba J. and Cesar O. Torres M.

Photonics 2019, 6(4), 121; https://doi.org/10.3390/photonics6040121 - 26 Nov 2019

Cited by 9 | Viewed by 3387

Abstract

We propose the use of the Jigsaw transform (JT) and the iterative cosine transform over a finite field in order to encrypt and decrypt images. The JT is a nonlinear operation that allows one to increase the security over the encrypted images by [...] Read more.

We propose the use of the Jigsaw transform (JT) and the iterative cosine transform over a finite field in order to encrypt and decrypt images. The JT is a nonlinear operation that allows one to increase the security over the encrypted images by adding new keys to the encryption and decryption systems. The finite field is a finite set of integer numbers where the basic mathematical operations are performed using modular arithmetic. The finite field used in the encryption and decryption systems has an order given by the Fermat prime number 257. The iterative finite field cosine transform (FFCT) was used in our work with the purpose of obtaining images that had an uniform random distribution. We used a security key given by an image randomly generated and uniformly distributed. The JT and iterative FFCT was utilized twice in the encryption and decryption systems. The encrypted images presented a uniformly distributed histogram and the decrypted images were the same original images used as inputs in the encryption system. The resulting decrypted images had a high level of image quality in comparison to the image quality of the decrypted images obtained by the actual optical decryption systems. The proposed encryption and decryption systems have three security keys represented by two random permutations used in the JTs and one random image. The key space of the proposed encryption and decryption systems is larger. The previous features of the security system allow a better protection of the encrypted image against brute force and statistical analysis attacks. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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9 pages, 917 KiB

Open AccessArticle

Image Processing Operators Based on the Gyrator Transform: Generalized Shift, Convolution and Correlation

by Ronal A. Perez, Juan M. Vilardy O. and Cesar O. Torres M.

Photonics 2019, 6(4), 120; https://doi.org/10.3390/photonics6040120 - 16 Nov 2019

Cited by 4 | Viewed by 3228

Abstract

The gyrator transform (GT) is used for images processing in applications of light propagation. We propose new image processing operators based on the GT, these operators are: Generalized shift, convolution and correlation. The generalized shift is given by a simultaneous application of a [...] Read more.

The gyrator transform (GT) is used for images processing in applications of light propagation. We propose new image processing operators based on the GT, these operators are: Generalized shift, convolution and correlation. The generalized shift is given by a simultaneous application of a spatial shift and a modulation by a pure linear phase term. The new operators of convolution and correlation are defined using the GT. All these image processing operators can be used in order to design and implement new optical image processing systems based on the GT. The sampling theorem for images whose resulting GT has finite support is developed and presented using the previously defined operators. Finally, we describe and show the results for an optical image encryption system using a nonlinear joint transform correlator and the proposed image processing operators based on the GT. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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8 pages, 7305 KiB

Open AccessArticle

Tunable THz Graphene Filter Based on Cross-In-Square-Shaped Resonators Metasurface

by Anton Zaitsev, Alexander Grebenchukov and Mikhail Khodzitsky

Photonics 2019, 6(4), 119; https://doi.org/10.3390/photonics6040119 - 12 Nov 2019

Cited by 17 | Viewed by 3454

Abstract

The tunable terahertz (THz) Fano-resonant filter based on hybrid metal-graphene metamaterial was proposed. The optical parameters of metasurface with unit cell in the form of a cross-shaped graphene sheet in the center of a square gold ring were simulated by the finite element [...] Read more.

The tunable terahertz (THz) Fano-resonant filter based on hybrid metal-graphene metamaterial was proposed. The optical parameters of metasurface with unit cell in the form of a cross-shaped graphene sheet in the center of a square gold ring were simulated by the finite element method using a surface conductivity model of a graphene monolayer. The narrowband modulation of the transmission by varying the Fermi level of the graphene and the position of graphene cross inside the metal ring was demonstrated. Simulation results were well explained theoretically using a three-coupled oscillator model. The proposed device can be used as a narrowband filter in wireless THz communication systems and sensing applications. Full article

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Scheme of the unit cell geometry: The graphene cross-like layer is located on the quartz substrate (with <math display="inline"><semantics> <mrow> <mi>ϵ</mi> <mo>=</mo> <mn>3</mn> <mo>.</mo> <mn>75</mn> </mrow> </semantics></math>) in its center and is surrounded by a square gold ring. G is the size of the unit cell, R and K is the external size and width of gold ring respectively, and L and D is the length and the width of graphene cross-like layer respectively. Full article ">Figure 2
On the left side: Transmittance spectra of the filter in the absence of the gold ring with a fixed graphene Fermi level of 0.5 eV (a), in the absence of the graphene layer (b), and in case of the full Fano-resonant structure under electrostatic doping of 0.5 eV (c). On the right side: Corresponding electric field distributions. Full article ">Figure 3
Transmission spectra of the filter for the different graphene Fermi level values from 0 eV to 0.5 eV (different gate voltage values). Full article ">Figure 4
Transmission spectra for theoretical and numerical calculations with increasing graphene Fermi level values from 0 eV to 0.5 eV (different gate voltage values) for graphene-based filter. Full article ">Figure 5
Transmission spectra of the filter with different unit cell structure: Original designed filter structure (a), structure with shifted graphene cross along one direction up to 100 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m (b), structure with shifted graphene cross along two directions up to 100 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m, and (c) graphene Fermi energy fixed at 0.5 eV. Full article ">

8 pages, 1477 KiB

Open AccessArticle

Lithographic Mask Defects Analysis on an MMI 3 dB Splitter

by Paulo Lourenço, Alessandro Fantoni, João Costa and Manuela Vieira

Photonics 2019, 6(4), 118; https://doi.org/10.3390/photonics6040118 - 9 Nov 2019

Cited by 7 | Viewed by 3645

Abstract

In this paper, we present a simulation study that intends to characterize the influence of defects introduced by manufacturing processes on the geometry of a semiconductor structure suitable to be used as a multimode interference (MMI) 3 dB power splitter. Consequently, these defects [...] Read more.

In this paper, we present a simulation study that intends to characterize the influence of defects introduced by manufacturing processes on the geometry of a semiconductor structure suitable to be used as a multimode interference (MMI) 3 dB power splitter. Consequently, these defects will represent refractive index fluctuations which, on their turn, will drastically affect the propagation conditions within the structure. Our simulations were conducted on a software platform that implements the Beam Propagation numerical method. This work supports the development of a biomedical plasmonic sensor, which is based on the coupling between propagating modes in a dielectric waveguide and the surface plasmon mode that is generated on an overlaid metallic thin film, and where the output readout is achieved through an a-Si:H photodiode. By using a multimode interference 1 × 2 power splitter, this sensor device can utilize the non-sensing arm as a reference one, greatly facilitating its calibration and enhancing its performance. As the spectral sensitivity of amorphous silicon is restricted to the visible range, this sensing device should be operating on a wavelength not higher than 700 nm; thus, a-SiNx has been the material hereby proposed for both waveguides and MMI power splitter. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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10 pages, 2320 KiB

Open AccessEditor’s ChoiceArticle

Biofunctionalized Polyelectrolyte Microcapsules Encoded with Fluorescent Semiconductor Nanocrystals for Highly Specific Targeting and Imaging of Cancer Cells

by Galina Nifontova, Daria Kalenichenko, Maria Baryshnikova, Fernanda Ramos Gomes, Frauke Alves, Alexander Karaulov, Igor Nabiev and Alyona Sukhanova

Photonics 2019, 6(4), 117; https://doi.org/10.3390/photonics6040117 - 8 Nov 2019

Cited by 9 | Viewed by 3964

Abstract

Fluorescent semiconductor nanocrystals or quantum dots (QDs) are characterized by unique optical properties, including a high photostability, wide absorption spectrum, and narrow, symmetric fluorescence spectrum. This makes them attractive fluorescent nanolabels for the optical encoding of microcarriers intended for targeted drug delivery, diagnosis, [...] Read more.

Fluorescent semiconductor nanocrystals or quantum dots (QDs) are characterized by unique optical properties, including a high photostability, wide absorption spectrum, and narrow, symmetric fluorescence spectrum. This makes them attractive fluorescent nanolabels for the optical encoding of microcarriers intended for targeted drug delivery, diagnosis, and imaging of transport processes on the body, cellular, and subcellular levels. Incorporation of QDs into carriers in the form of polyelectrolyte microcapsules through layer-by-layer adsorption of oppositely charged polyelectrolyte polymers yields microcapsules with a bright fluorescence signal and adaptable size, structure, and surface characteristics without using organic solvents. The easily modifiable surface of the microcapsules allows for its subsequent functionalization with capture molecules, such as antibodies, which ensures specific and selective interaction with cells, including tumor cells, with the use of the bioconjugation technique developed here. We obtained stable water-soluble nanolabels based on QDs whose surface was modified with polyethylene glycol (PEG) derivatives and determined their colloidal and optical characteristics. The obtained nanocrystals were used to encode polyelectrolyte microcapsules optically. The microcapsule surface was modified with humanized monoclonal antibodies (Abs) recognizing a cancer marker, epidermal growth factor receptor (EGFR). The possibility of effective, specific, and selective delivery of the microcapsules to tumor cells expressing EGFR has been demonstrated. The results show that the QD-encoded polyelectrolyte microcapsules functionalized with monoclonal Abs against EGFR can be used for targeted imaging and diagnosis. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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Polyelectrolyte shell formation and optical encoding with quantum dots (QDs) using a layer-by-layer deposition: (a) the scheme of the polyelectrolyte and QD deposition onto the calcium carbonate microparticle surface; (b) microphotographs of the synthesized calcium carbonate template microparticles (1) and resultant QD-encoded microcapsules (2). The fluorescent image was obtained using an XF115-2 FITC long pass filter set consisting of a 505DRLP dichroic filter, a 475AF40 excitation filter, and a 510ALP emission filter. Full article ">Figure 2
Efficiency of the microcapsule staining using trypan blue: * the data are significantly different from 4, 6, 8, 16, 32 h (p < 0.05); ** the data are significantly different from 6, 8, 16, 32 h (p < 0.05); *** the data are significantly different from 8 and 32 h (p < 0.05). Full article ">Figure 3
Coupling of antibodies to the microcapsule surface: (a) the scheme of the microcapsule surface activation (1) and antibody coupling (2); (b) antibody coupling efficiency, the data on the coupling yield are presented in the inset. Full article ">Figure 4
General view of the MDA-MB-468 human breast adenocarcinoma cells interacting with the antibody-functionalized, quantum dot-encoded microcapsules. Full article ">Figure 5
Images of individual cancer cells or their groups interacting with the QD-encoded microcapsules ((1) antibody-functionalized microcapsules; (2) bovine serum albumin-coated microcapsules): (a) MDA-MB-468 human breast adenocarcinoma cells; (b) MCF-7 human breast adenocarcinoma cells. Full article ">

7 pages, 1140 KiB

Open AccessArticle

Optical Image Encryption System Using Several Tilted Planes

by Juan M. Vilardy O., Carlos J. Jimenez and Cesar O. Torres M.

Photonics 2019, 6(4), 116; https://doi.org/10.3390/photonics6040116 - 7 Nov 2019

Cited by 6 | Viewed by 3162

Abstract

A well-known technique for optical image encryption is the double random phase encoding (DRPE) technique, which uses two random phase masks (RPMs), one RPM at the input plane of the encryption system and the other RPM at the Fourier plane of the optical [...] Read more.

A well-known technique for optical image encryption is the double random phase encoding (DRPE) technique, which uses two random phase masks (RPMs), one RPM at the input plane of the encryption system and the other RPM at the Fourier plane of the optical system, in order to obtain the encrypted image. In this work, we propose to use tilted planes for the Fourier and the output planes of the optical DRPE encryption system with the purpose of adding two new security keys, which are the angles of the tilted planes. The optical diffraction on a tilted plane is computed using the angular spectrum of plane waves and the coordinate rotation in the Fourier domain. The tilted distributions at the intermediate and output planes of the optical DRPE encryption system are the second RPM and the encrypted image, respectively. The angles of the tilted planes allow improvement to the security of the encrypted image. We perform several numerical simulations with the purpose of demonstrating the validity and feasibility of the proposed image encryption system. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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9 pages, 2613 KiB

Open AccessArticle

Optical Image Encryption Using a Nonlinear Joint Transform Correlator and the Collins Diffraction Transform

by Juan M. Vilardy O., Ronal A. Perez and Cesar O. Torres M.

Photonics 2019, 6(4), 115; https://doi.org/10.3390/photonics6040115 - 7 Nov 2019

Cited by 7 | Viewed by 3128

Abstract

The Collins diffraction transform (CDT) describes the optical wave diffraction from the generic paraxial optical system. The CDT has as special cases the diffraction domains given by the Fourier, Fresnel and fractional Fourier transforms. In this paper, we propose to describe the optical [...] Read more.

The Collins diffraction transform (CDT) describes the optical wave diffraction from the generic paraxial optical system. The CDT has as special cases the diffraction domains given by the Fourier, Fresnel and fractional Fourier transforms. In this paper, we propose to describe the optical double random phase encoding (DRPE) using a nonlinear joint transform correlator (JTC) and the CDT. This new description of the nonlinear JTC-based encryption system using the CDT covers several optical processing domains, such as Fourier, Fresnel, fractional Fourier, extended fractional Fourier and Gyrator domains, among others. The maximum number of independent design parameters or new security keys of the proposed encryption system using the CDT increases three times in comparison with the same encryption system that uses the Fourier transform. The proposed encryption system using the CDT preserves the shift-invariance property of the JTC-based encryption system in the Fourier domain, with respect to the lateral displacement of both the key random mask in the decryption process and the retrieval of the primary image. The viability of this encryption system is verified and analysed by numerical simulations. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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16 pages, 1034 KiB

Open AccessEditor’s ChoiceArticle

Pupil Function in Pseudophakia: Proximal Miosis Behavior and Optical Influence

by Elsa Fonseca, Paulo Fiadeiro, Renato Gomes, Angel Sanchez Trancon, António Baptista and Pedro Serra

Photonics 2019, 6(4), 114; https://doi.org/10.3390/photonics6040114 - 6 Nov 2019

Cited by 2 | Viewed by 5552

Abstract

The pseudophakic eye lacks the ability to produce a refractive change in response to object proximity. Thus, individual anatomical features such as the pupil size play an important role in achieving functional vision levels. In this work, the range of pupil sizes at [...] Read more.

The pseudophakic eye lacks the ability to produce a refractive change in response to object proximity. Thus, individual anatomical features such as the pupil size play an important role in achieving functional vision levels. In this work, the range of pupil sizes at varying object distance was measured in pseudophakic participants. Furthermore, the impact of the measured values on eye optical quality was investigated using a computer simulation model. A binocular eye-tracker was used to measure the participants’ pupil sizes at six object distances, ranging from

0.33

m (i.e., vergence of

3.00

D) to

3.00

m (i.e., vergence of

0.33

D), while observing a Maltese cross with a constant angular size of

1^{\circ}

. In total, 58 pseudophakic participants were enrolled in this study (age mean ± standard deviation:

70.5 \pm 11.3

years). The effects of object distance and age on pupil size variation were investigated using linear mixed effects regression models. Age was found to have a small contribution to individual variability. The mean infinite distance pupil size (intercept) was

4.45

(

95 %

CI: 2.74, 6.17) mm and the mean proximal miosis (slope) was

- 0.23

(

95 %

CI: −0.53, 0.08) mm/D. The visual acuity (VA) estimation for a distant object ranged from

- 0.1

logMAR (smallest pupil) to

0.04

logMAR (largest pupil) and the near VA (

0.33

m) when mean proximal miosis was considered ranged from

0.28

logMAR (smallest pupil) to

0.42

logMAR (largest pupil). When mean distance pupil was considered, proximal miosis individual variability produced a variation of

0.04

logMAR for the near object and negligible variation for the distant object. These results support the importance of distance pupil size measurement for the prediction of visual performance in pseudophakia, while suggesting that proximal miosis has a negligible impact in VA variability. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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Pupil diameter recordings during 15 s and for the different observing distances. Upper set: The raw data for the RE and LE. Lower set: The pupil sizes after blink removal for the RE and LE using the Hampel filter. Full article ">Figure 2
(a) Far distance (<math display="inline"><semantics> <mrow> <mn>3.0</mn> </mrow> </semantics></math> m) pupil diameter versus subjective spherical equivalent. (b) Far distance (<math display="inline"><semantics> <mrow> <mn>3.0</mn> </mrow> </semantics></math> m) pupil diameter versus age. Full article ">Figure 3
(a) Fixed effect fit and <math display="inline"><semantics> <mrow> <mn>95</mn> <mo>%</mo> </mrow> </semantics></math> confidence limits for the mean (dashed green line) and for a single prediction (dashed red line) for a given value of pupil diameter. (b) Scatter plot of standardized residuals versus fitted values for the first mixed effects model. Full article ">Figure 4
Area under MTF as a function of object vergence in diopters, from near (<math display="inline"><semantics> <mrow> <mi>O</mi> <mi>V</mi> <mo>=</mo> <mo>−</mo> <mn>3</mn> <mspace width="0.277778em"/> <mi mathvariant="normal">D</mi> </mrow> </semantics></math>) to far (<math display="inline"><semantics> <mrow> <mi>O</mi> <mi>V</mi> <mo>=</mo> <mn>0</mn> <mspace width="0.277778em"/> <mi mathvariant="normal">D</mi> </mrow> </semantics></math>) object distances: (a) Case 1 models with constant pupil miosis and varying distance pupil diameter (PD) values; and (b) Case 2 models with constant distance pupil and varying pupil miosis. Full article ">Figure 5
Predicted visual acuity in logMAR (MAR: Minimum Angle of resolution) variation as function of object vergence in diopters, using the simulated area under MTF curve and Equation (<a href="#FD10-photonics-06-00114" class="html-disp-formula">10</a>), from near (<math display="inline"><semantics> <mrow> <mi>O</mi> <mi>V</mi> <mo>=</mo> <mo>−</mo> <mn>3</mn> <mspace width="0.277778em"/> <mi mathvariant="normal">D</mi> </mrow> </semantics></math>) to far (<math display="inline"><semantics> <mrow> <mi>O</mi> <mi>V</mi> <mo>=</mo> <mn>0</mn> <mspace width="0.277778em"/> <mi mathvariant="normal">D</mi> </mrow> </semantics></math>) object distances: (a) Case 1 models with constant pupil miosis and varying distance pupil diameter (PD) values; and (b) Case 2 models with constant distance pupil and varying pupil miosis. Full article ">

8 pages, 3479 KiB

Open AccessArticle

Ultrafast All-Optical Signal Modulation Induced by Optical Kerr Effect in a Tellurite Photonic Bandgap Fiber

by Tonglei Cheng, Fan Zhang, Shunta Tanaka, Shuguang Li, Xin Yan, Xuenan Zhang, Takenobu Suzuki and Yasutake Ohishi

Photonics 2019, 6(4), 113; https://doi.org/10.3390/photonics6040113 - 29 Oct 2019

Cited by 6 | Viewed by 3399

Abstract

Ultrafast all-optical signal modulation induced by optical Kerr effect (OKE) was demonstrated in an all-solid tellurite photonic bandgap fiber (PBGF) which was designed and fabricated based on TeO₂-Li₂O-WO₃-MoO₃-Nb₂O₅ (TLWMN, high-index rods), TeO [...] Read more.

Ultrafast all-optical signal modulation induced by optical Kerr effect (OKE) was demonstrated in an all-solid tellurite photonic bandgap fiber (PBGF) which was designed and fabricated based on TeO₂-Li₂O-WO₃-MoO₃-Nb₂O₅ (TLWMN, high-index rods), TeO₂-ZnO-Na₂O-La₂O₃ (TZNL, background), and TeO₂-ZnO-Li₂O-K₂O-Al₂O₃-P₂O₅ (TZLKAP, cladding) glasses. At the input of a control pulse with high intensity, OKE occurred in the tellurite PBGF and the transmission bands of the tellurite PBGF shifted. The signal at 1.57 μm transmitting in the fiber core can be ultrafast all-optically modulated by the ultrafast single pulse (200 kW, 200 fs) under OKE, where the modulation speed can reach 50 GHz, faster than some commercial LiNbO₃ modulators. The results in this paper can be applied to multi-monitors, local area network, detectors, multi-sources, etc. Full article

(This article belongs to the Special Issue Advanced Optical Materials and Devices)

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(a) Control beam with intensity Iin transmitting in the core of an all-solid PBGF. (b) BPG regions appear from 1.0 μm to 2.0 μm. (c) Schematic diagram of the transmission shift induced by OKE in an all-solid tellurite PBGF. Full article ">Figure 2
Spectra of TLWMN, TZNL, and TZLKAP glasses. Full article ">Figure 3
Fabrication process of the all-solid double-clad tellurite PBGF. (a) TLWMN and TZNL capillary. (b) Capillary with TLWMN core. (c) Fabricated the optical fibers. Full article ">Figure 4
PBG map of the all-solid double-clad tellurite PBGF at d/Λ = 0.6. Full article ">Figure 5
Calculated transmission spectrum of the all-solid double-clad tellurite PBGF with the control pulse power increasing from 0 to 300 kW. Full article ">Figure 6
Schematic diagram of the all-optical signal modulation controlled by the ultrafast single pulse. Full article ">Figure 7
(a) Experimental setup for investigating the all-optical signal modulation controlled by the ultrafast single pulse in the all-solid double-clad tellurite PBGF. (b) Experimental results of the all-optical signal modulation controlled by the ultrafast single pulse. Full article ">

11 pages, 4447 KiB

Open AccessArticle

Optical Feedback Sensitivity of a Semiconductor Ring Laser with Tunable Directionality

by Guy Verschaffelt, Mulham Khoder and Guy Van der Sande

Photonics 2019, 6(4), 112; https://doi.org/10.3390/photonics6040112 - 28 Oct 2019

Cited by 9 | Viewed by 3286

Abstract

We discuss the sensitivity to optical feedback of a semiconductor ring laser that is made to emit in a single-longitudinal mode by applying on-chip filtered optical feedback in one of the directional modes. The device is fabricated on a generic photonics integration platform [...] Read more.

We discuss the sensitivity to optical feedback of a semiconductor ring laser that is made to emit in a single-longitudinal mode by applying on-chip filtered optical feedback in one of the directional modes. The device is fabricated on a generic photonics integration platform using standard components. By varying the filtered feedback strength, we can tune the wavelength and directionality of the laser. Beside this, filtered optical feedback results in a limited reduction of the sensitivity for optical feedback from an off-chip optical reflection when the laser is operating in the unidirectional regime. Full article

(This article belongs to the Special Issue Semiconductor Laser Dynamics: Fundamentals and Applications)

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17 pages, 3620 KiB

Open AccessArticle

Monitoring of OSNR Using an Improved Binary Particle Swarm Optimization and Deep Neural Network in Coherent Optical Systems

by Xiaoyong Sun, Shaojing Su, Junyu Wei, Xiaojun Guo and Xiaopeng Tan

Photonics 2019, 6(4), 111; https://doi.org/10.3390/photonics6040111 - 25 Oct 2019

Cited by 7 | Viewed by 3704

Abstract

A novel technique is proposed to implement optical signal-to-noise ratio (OSNR) estimation by using an improved binary particle swarm optimization (IBPSO) and deep neural network (DNN) based on amplitude histograms (AHs) of signals obtained after constant modulus algorithm (CMA) equalization in an optical [...] Read more.

A novel technique is proposed to implement optical signal-to-noise ratio (OSNR) estimation by using an improved binary particle swarm optimization (IBPSO) and deep neural network (DNN) based on amplitude histograms (AHs) of signals obtained after constant modulus algorithm (CMA) equalization in an optical coherent system. For existing OSNR estimation models of DNN and AHs, sparse AHs with valid features of original data are selected by IBPSO algorithm to replace the original, and the sparse sets are used as input vector to train and test the particle swarm optimization (PSO) optimized DNN (PSO-DNN) network structure. Numerical simulations have been carried out in the OSNR ranges from 10 dB to 30 dB for 112 Gbps PM-RZ-QPSK and 112 Gbps PM-NRZ-16QAM signals, and results show that the proposed algorithm achieves a high OSNR estimation accuracy with the maximum estimation error is less than 0.5 dB. In addition, the simulation results with different data input into the deep neural network structure show that the mean OSNR estimation error is 0.29 dB and 0.39 dB under original data and 0.29 dB and 0.37 dB under sparse data for the two signals, respectively. In the future dynamic optical network, it is of more practical significance to reconstruct the original signal and analyze the data using sparse observation information in the face of multiple impairment and serious interference. The proposed technique has the potential to be applied for optical performance monitoring (OPM) and is helpful for better management of optical networks. Full article

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10 pages, 3003 KiB

Open AccessArticle

Photostable Anisometric Lanthanide Complexes as Promising Materials for Optical Applications

by Andrey Knyazev, Maxim Karyakin and Yuriy Galyametdinov

Photonics 2019, 6(4), 110; https://doi.org/10.3390/photonics6040110 - 25 Oct 2019

Cited by 10 | Viewed by 3981

Abstract

Uniform luminescent films with high optical quality are promising materials for modern molecular photonics. Such film materials based on β-diketonate complexes of lanthanides have the following application problem: rapid luminescence degradation under UV radiation, low thermostability, poor mechanical properties, and aggregation propensity. An [...] Read more.

Uniform luminescent films with high optical quality are promising materials for modern molecular photonics. Such film materials based on β-diketonate complexes of lanthanides have the following application problem: rapid luminescence degradation under UV radiation, low thermostability, poor mechanical properties, and aggregation propensity. An alternative approach to solving these problems is the use of anisometric analogues of β-diketonate compounds of lanthanides (III). The main advantage of such compounds is that they do not crystallize because of long hydrocarbon substituents in the structure of complexes, so they can be used to fabricate thin nano-, micro-, and macroscale uniform film materials by a melt-processing technique at relatively low temperatures, as well as by spin-coating. The method of fabrication of microscale luminescent film materials with controlled optical properties from anisometric analogues of Ln(DBM)₃Phen and Ln(bzac)₃Phen complexes (Ln = Eu, Tb) is proposed in this paper. Within the framework of this research, we developed original films which are highly uniform and transparent. An important advantage of these films is their high photostability and potential for applications as reusable luminescent sensors and light converters. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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11 pages, 5189 KiB

Open AccessArticle

A Refractive Index Sensor Based on a Fabry–Perot Interferometer Manufactured by NIR Laser Microdrilling and Electric Arc Fusion

by Marta Nespereira, João M. P. Coelho and José M. Rebordão

Photonics 2019, 6(4), 109; https://doi.org/10.3390/photonics6040109 - 24 Oct 2019

Cited by 4 | Viewed by 3673

Abstract

In-line Fabry–Perot cavities manufactured by a new technique using electric arc fusion of NIR laser microdrilled optical fiber flat tips were studied herein for refractive index sensing. Sensors were produced by creating an initial hole on the tip of a standard single-mode telecommunication [...] Read more.

In-line Fabry–Perot cavities manufactured by a new technique using electric arc fusion of NIR laser microdrilled optical fiber flat tips were studied herein for refractive index sensing. Sensors were produced by creating an initial hole on the tip of a standard single-mode telecommunication optical fiber using a Q-switched Nd:YAG laser. Laser ablation and plasma formation processes created 5 to 10 micron cavities. Then, a standard splicing machine was used to fuse the microdrilled fiber with another one, thus creating cavities with lengths around 100 micrometers. This length has been proven to be necessary to obtain an interferometric signal with good fringe visibility when illuminating it in the C-band. Then, the sensing tip of the fiber, with the resulting air cavity, was submitted to several cleaves to enhance the signal and, therefore, its response as a sensor, with final lengths between tens of centimeters for the longest and hundreds of microns for the shortest. The experimental results were analyzed via two signal analysis techniques, fringe visibility and fast Fourier transform, for comparison purposes. In absolute values, the obtained sensitivities varied between 0.31 nm⁻¹/RIU and about 8 nm⁻¹/RIU using the latter method and between about 34 dB/RIU and 54 dB/RIU when analyzing the fringe visibility. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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14 pages, 3135 KiB

Open AccessArticle

Enhanced Biosensing Activity of Bimetallic Surface Plasmon Resonance Sensor

by Ritayan Kashyap, Soumik Chakraborty, Shuwen Zeng, Sikha Swarnakar, Simran Kaur, Robin Doley and Biplob Mondal

Photonics 2019, 6(4), 108; https://doi.org/10.3390/photonics6040108 - 21 Oct 2019

Cited by 34 | Viewed by 4827

Abstract

Surface plasmon resonance (SPR) sensors present a challenge when high sensitivity and small FWHM (full width at half maximum) are required to be achieved simultaneously. FWHM is defined by the difference between the two extreme values of the independent variable at which the [...] Read more.

Surface plasmon resonance (SPR) sensors present a challenge when high sensitivity and small FWHM (full width at half maximum) are required to be achieved simultaneously. FWHM is defined by the difference between the two extreme values of the independent variable at which the value of the dependent variable is equal to half of its maximum. A smaller value of FWHM indicates better accuracy of SPR measurements. Theoretically, many authors have claimed the possibility of simultaneously achieving high sensitivity and small FWHM, which in most of the cases has been limited by experimental validation. In this report, an experimental study on the improved surface plasmon resonance (SPR) characteristics of gold over silver bimetallic sensor chips of different film thicknesses is presented. A comparative study of antigen–antibody interaction of the bimetallic chip using a custom-made, low-cost, and portable SPR device based on an angular interrogation scheme of Kretschmann configuration is performed. Pulsed direct current (DC) magnetron-sputtered bimetallic films of gold over silver were used in the construction of the SPR chip. The FWHM and sensitivity of the bimetallic sensors were firstly characterized using standard solutions of known refractive index which were later immobilized with monoclonal anti-immunoglobulin G (IgG) in the construction of the SPR biochip. Spectroscopic measurements such as ultraviolet–visible light spectroscopy (UV–Vis) and Fourier-transform infrared spectroscopy (FTIR) were used for the confirmation of the immobilization of the antibody. The performance of the bimetallic SPR biochip was investigated by exposing the sensor to various concentrations of the target protein. The results indicated that the bimetallic sensors of silver/gold had a 3.5-fold reduced FWHM compared to pure gold-based sensors, indicating a higher detection accuracy. In addition, they exhibited a significant shift in resonance angle as high as 8.5 ± 0.2 due to antigen–antibody interaction, which was ~1.42-fold higher than observed for pure silver-based sensors. Full article

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8 pages, 3098 KiB

Open AccessArticle

Monitoring of the Mechanism of Mn Ions Incorporation into Quantum Dots by Optical and EPR Spectroscopy

by Yuriy G. Galyametdinov, Dmitriy O. Sagdeev, Andrey A. Sukhanov, Violeta K. Voronkova and Radik R. Shamilov

Photonics 2019, 6(4), 107; https://doi.org/10.3390/photonics6040107 - 19 Oct 2019

Cited by 9 | Viewed by 3350

Abstract

Synthesis of nanoparticles doped with various ions can significantly expand their functionality. The conditions of synthesis exert significant influence on the distribution nature of doped ions and therefore the physicochemical properties of nanoparticles. In this paper, a correlation between the conditions of synthesis [...] Read more.

Synthesis of nanoparticles doped with various ions can significantly expand their functionality. The conditions of synthesis exert significant influence on the distribution nature of doped ions and therefore the physicochemical properties of nanoparticles. In this paper, a correlation between the conditions of synthesis of manganese-containing cadmium sulfide or zinc sulfide nanoparticles and their optical and magnetic properties is analyzed. Electron paramagnetic resonance was used to study the distribution of manganese ions in nanoparticles and the intensity of interaction between them depending on the conditions of synthesis of nanoparticles, the concentration of manganese, and the type of initial semiconductor. The increase of manganese concentration is shown to result in the formation of smaller CdS-based nanoparticles. Luminescent properties of nanoparticles were studied. The 580 nm peak, which is typical for manganese ions, becomes more distinguished with the increase of their concentration and the time of synthesis. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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Size distribution diagrams of quantum dot (QD) samples collected when the temperature reached 220 °C and 60 min later: (a) Cd0.9Mn0.1S; (b) Zn0.9Mn0.1S. Full article ">Figure 2
Diffraction patterns of Cd0.9Mn0.1S and Zn0.9Mn0.1S nanoparticles collected after 60 min of synthesis. Full article ">Figure 3
Absorption spectra of Cd0.9Mn0.1S nanoparticles at various synthesis times. Full article ">Figure 4
Luminescence spectra of QDs taken at various times after the start of synthesis: (a) Cd0.9Mn0.1S; (b) Zn0.9Mn0.1S. Full article ">Figure 5
(a) Luminescence spectra of Cd0.94Mn0.06S QDs taken at various times after the start of synthesis; (b) the dependence of the CdxMn1-xS luminescence collected after 60 min of synthesis on the amount of manganese ions. Full article ">Figure 6
Electron paramagnetic resonance (EPR) spectra of samples taken at various times after the start of synthesis: (a) Cd0.9Mn0.1S; (b) Zn0.9Mn0.1S. Full article ">Figure 7
(a) EPR spectra of the of Cd0.94Mn0.06S and Cd0.99Mn0.01S samples collected 60 min after the start of synthesis. (b) The model of Mn ions distribution in the CdS nanoparticles, Mnag are Mn ions in spin–spin interactions, Mncrys are single Mn ions in the crystal lattice. Full article ">

13 pages, 864 KiB

Open AccessArticle

Objective User Visual Experience Evaluation When Working with Virtual Pixel-Based 3D System and Real Voxel-Based 3D System

by Karola Panke, Tatjana Pladere, Mara Velina, Aiga Svede and Gunta Krumina

Photonics 2019, 6(4), 106; https://doi.org/10.3390/photonics6040106 - 16 Oct 2019

Cited by 1 | Viewed by 3212

Abstract

Volumetric display shows promising implications for healthcare related applications as an innovative technology that creates real three-dimensional (3D) image by illuminating points in three-dimensional space to generate volumetric images without image separation. We used eccentric photorefractometry to objectively study ocular performance in a [...] Read more.

Volumetric display shows promising implications for healthcare related applications as an innovative technology that creates real three-dimensional (3D) image by illuminating points in three-dimensional space to generate volumetric images without image separation. We used eccentric photorefractometry to objectively study ocular performance in a practical environment by evaluating near work-induced refraction shift, accommodative microfluctuations, and pupil size for 38 young adults after viewing anaglyph, and volumetric 3D content for prolonged time. The results of our study demonstrate that participants who performed relative depth estimation task on volumetric 3D content were less likely to experience task-induced myopic refraction shift. For both 3D content types, we observed pupil constriction, that is possibly related to visual fatigue. For anaglyph 3D pupil constriction, onset was observed significantly sooner, compared to volumetric 3D. Overall, sustained work with 3D content, and small disparities or the fully eliminated possibility of accommodation-vergence conflict, not only minimizes near work-induced myopic shift, but also provide beneficial accommodation relaxation that was demonstrated in this study as hypermetropic shift for nearly half of participants. Full article

(This article belongs to the Special Issue Advances on Applications of Optics and Photonics – Selected Papers from the 4th International Conference on Applications of Optics and Photonics, AOP2019)

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20 pages, 9453 KiB

Open AccessFeature PaperArticle

Incandescent Light Bulbs Based on a Refractory Metasurface

by Hirofumi Toyoda, Kazunari Kimino, Akihiro Kawano and Junichi Takahara

Photonics 2019, 6(4), 105; https://doi.org/10.3390/photonics6040105 - 12 Oct 2019

Cited by 12 | Viewed by 5986

Abstract

A thermal radiation light source, such as an incandescent light bulb, is considered a legacy light source with low luminous efficacy. However, it is an ideal energy source converting light with high efficiency from electric power to radiative power. In this work, we [...] Read more.

A thermal radiation light source, such as an incandescent light bulb, is considered a legacy light source with low luminous efficacy. However, it is an ideal energy source converting light with high efficiency from electric power to radiative power. In this work, we evaluate a thermal radiation light source and propose a new type of filament using a refractory metasurface to fabricate an efficient light bulb. We demonstrate visible-light spectral control using a refractory metasurface made of tantalum with an optical microcavity inserted into an incandescent light bulb. We use a nanoimprint method to fabricate the filament that is suitable for mass production. A 1.8 times enhancement of thermal radiation intensity is observed from the microcavity filament compared to the flat filament. Then, we demonstrate the thermal radiation control of the metasurface using a refractory plasmonic cavity made of hafnium nitride. A single narrow resonant peak is observed at the designed wavelength as well as the suppression of thermal radiation in wide mid-IR range under the condition of constant surface temperature. Full article

(This article belongs to the Special Issue Photonic Crystal Laser and Related Optical Devices)

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18 pages, 9265 KiB

Open AccessArticle

Irregular Shifting of RF Driving Signal Phase to Overcome Dispersion Power Fading

by Febrizal Ujang, Teguh Firmansyah, Purnomo S. Priambodo and Gunawan Wibisono

Photonics 2019, 6(4), 104; https://doi.org/10.3390/photonics6040104 - 12 Oct 2019

Cited by 4 | Viewed by 4410

Abstract

The main problem with the radio-over-fiber (RoF) link is the decrease in the recovered radio frequency (RF) power due to the chromatic dispersion of the fiber known as dispersion power fading. One of the methods for dealing with dispersion power fading is to [...] Read more.

The main problem with the radio-over-fiber (RoF) link is the decrease in the recovered radio frequency (RF) power due to the chromatic dispersion of the fiber known as dispersion power fading. One of the methods for dealing with dispersion power fading is to use the optical single sideband (OSSB) modulation scheme. The OSSB modulation scheme can be generated by biasing the dual-drive Mach–Zehnder modulator (DD-MZM) to the quadrature bias point (QBP) and shifting the RF drive signal phase (θ) by 90°, which is called the regular θ. However, the OSSB modulation scheme only overcomes dispersion power fading well at the modulation index (m) < 0.2. This paper proposes an irregular θ method to overcome dispersion power fading at all m. There are two irregular θ for every m used. The irregular θ managed to handle dispersion power fading better than OSSB modulation scheme did at every m. Specifically, the irregular θ could handle the dispersion power fading well at m ≤ 1. In sum, the irregular θ could overcome the dispersion power fading at any RF frequency and optical wavelength without having to re-adjust the transmitter. Full article

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14 pages, 5918 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Comparison between off and On-Chip Injection Locking in a Photonic Integrated Circuit

by Alison H. Perrott, Ludovic Caro, Mohamad Dernaika and Frank H. Peters

Photonics 2019, 6(4), 103; https://doi.org/10.3390/photonics6040103 - 1 Oct 2019

Cited by 8 | Viewed by 3666

Abstract

The mutual and injection locking characteristics of two integrated lasers are compared, both on and off-chip. In this study, two integrated single facet slotted Fabry–Pérot lasers are utilised to develop the measurement technique used to examine the different operational regimes arising from optically [...] Read more.

The mutual and injection locking characteristics of two integrated lasers are compared, both on and off-chip. In this study, two integrated single facet slotted Fabry–Pérot lasers are utilised to develop the measurement technique used to examine the different operational regimes arising from optically locking a semiconductor diode laser. The technique employed used an optical spectrum analyser (OSA), an electrical spectrum analyser (ESA) and a high speed oscilloscope (HSO). The wavelengths of the lasers are measured on the OSA and the selected optical mode for locking is identified. The region of injection locking and various other regions of dynamical behaviour between the lasers are observed on the ESA. The time trace information of the system is obtained from the HSO and performing the FFT (Fast Fourier Transform) of the time traces returns the power spectra. Using these tools, the similarities and differences between off-chip injection locking with an isolator, and on-chip mutual locking are examined. Full article

(This article belongs to the Special Issue Semiconductor Laser Dynamics: Fundamentals and Applications)

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9 pages, 2488 KiB

Open AccessArticle

A Monolithically Integrated Laser-Photodetector Chip for On-Chip Photonic and Microwave Signal Generation

by Hefei Qi, Guangcan Chen, Dan Lu and Lingjuan Zhao

Photonics 2019, 6(4), 102; https://doi.org/10.3390/photonics6040102 - 30 Sep 2019

Cited by 5 | Viewed by 4088

Abstract

An Indium-phosphide-based monolithically integrated photonic chip comprising of an amplified feedback laser (AFL) and a photodetector was designed and fabricated for on-chip photonic and microwave generation. Various waveforms including single tone, multi-tone, and chaotic signal generation were demonstrated by simply adjusting the injection [...] Read more.

An Indium-phosphide-based monolithically integrated photonic chip comprising of an amplified feedback laser (AFL) and a photodetector was designed and fabricated for on-chip photonic and microwave generation. Various waveforms including single tone, multi-tone, and chaotic signal generation were demonstrated by simply adjusting the injection currents applied to the controlling electrodes. The evolution dynamics of the photonic chip was characterized. Photonic microwave with frequency separation tunable from 26.3 GHz to 34 GHz, chaotic signal with standard bandwidth of 12 GHz were obtained. An optoelectronic oscillator (OEO) based on the integrated photonic chip was demonstrated without using any external electrical filter and photodetector. Tunable microwave outputs ranging from 25.5 to 26.4 GHz with single sideband (SSB) phase noise less than −90 dBc/Hz at a 10-kHz offset from the carrier frequency were realized. Full article

(This article belongs to the Special Issue Semiconductor Laser Dynamics: Fundamentals and Applications)

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(a) Microscopic picture; (b) schematic diagram; and (c) test system diagram of the integrated laser-photodetector chip. EA: electrical amplifier; EC: electrical coupler; OSA: optical Spectrum analyzer; OSC: oscilloscope; ESA: electrical spectrum analyzer). Full article ">Figure 2
Various dynamic states of the output of the integrated laser-photodetector chip at VPD = −2.5 V, IDFB = 78 mA, IPhase = 3 mA when IA varies from top to bottoms as (a) 0 mA (S state); (b) 9 mA (P1 state); (c) 18.5 mA (C state); (d) 24.5 mA (D state). (a-i)–(d-i): optical spectra, (a-ii)–(d-ii): RF spectra, (a-iii)–(d-iii): temporal waveforms, and (a-iv)–(d-iv): phase portraits of various dynamic states, respectively. Full article ">Figure 3
When VPD, IDFB, and Iphase were fixed at −2.5 V, 78 mA, and 3 mA, respectively, (a) the RF spectra with IA = 42.5 mA, Inset: 100-MHz zoom-in view; and (b) the beating RF frequency when IA varied from 24.5 mA to 50.5 mA. Full article ">Figure 4
Schematic diagram of the optoelectronic oscillator (OEO) based on the integrated laser-photodetector chip. EA, electrical amplifier; OC, optical coupler; EC, electrical coupler; Cir, circulator; MZM, Mach-Zehnder modulator; PC, polarization controller; VOA, variable optical attenuator; OSA, optical spectrum analyzer; ESA, electrical spectrum analyzer. Full article ">Figure 5
(a) The RF output from the OEO, Inset: zoom-in view in a frequency range of 1 MHz; (b) single sideband (SSB) phase noise spectrum of the generated 26.05 GHz microwave signal. Full article ">Figure 6
The OEO’s (a) RF spectrum; (b) SSB phase noise at the 10 kHz offset from the carrier frequency, with IA varied from 40 mA to 46 mA, when VPD, IDFB, and IPhase were fixed at −2.5 V, 75 mA, and 1.5 mA. Full article ">

13 pages, 7165 KiB

Open AccessEditor’s ChoiceArticle

Flowline Optical Simulation to Refractive/Reflective 3D Systems: Optical Path Length Correction

by Angel García-Botella, Lun Jiang and Roland Winston

Photonics 2019, 6(4), 101; https://doi.org/10.3390/photonics6040101 - 28 Sep 2019

Cited by 6 | Viewed by 3138

Abstract

Nonimaging optics is focused on the study of techniques to design optical systems for the purpose of energy transfer instead of image forming. The flowline optical design method, based on the definition of the geometrical flux vector J, is one of these [...] Read more.

Nonimaging optics is focused on the study of techniques to design optical systems for the purpose of energy transfer instead of image forming. The flowline optical design method, based on the definition of the geometrical flux vector J, is one of these techniques. The main advantage of the flowline method is its capability to visualize and estimate how radiant energy is transferred by the optical systems using the concepts of vector field theory, such as field line or flux tube, which overcomes traditional raytrace methods. The main objective this paper is to extend the flowline method to analyze and design real 3D concentration and illumination systems by the development of new simulation techniques. In this paper, analyzed real 3D refractive and reflective systems using the flowline vector potential method. A new constant term of optical path length is introduced, similar and comparable to the gauge invariant, which produces a correction to enable the agreement between raytrace- and flowline-based computations. This new optical simulation methodology provides traditional raytrace results, such as irradiance maps, but opens new perspectives to obtaining higher precision with lower computation time. It can also provide new information for the vector field maps of 3D refractive/reflective systems. Full article

(This article belongs to the Special Issue Nonimaging Optics in Solar Energy)

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