Sub-area design of reflective metasurfaces for Bessel beam generation to mitigate the impact of feed occlusion

Hao Honggang, Ting Zhang, Dan Yin, and Jinfeng He

DOI: 10.1364/AO.533778 Received 25 Jun 2024; Accepted 08 Aug 2024; Posted 08 Aug 2024  View: PDF

Abstract: This paper introduces a sub-area metasurface designed to mitigate the effects of feedocclusion when generating Bessel beams on reflective metasurfaces. This unit incorporates ananisotropic structure with distinct phase responses tailored for two orthogonal linearly polarised(LP) electromagnetic (EM) waves. The energy loss of the Bessel beam, situated behind the feedsource, generated by the outer ring is minimized, through the superposition of the inwardtraveling waves and strategic partitioning of the array area. Furthermore, the principle ofelectric field superposition is employed to focus on the inner ring. The simulated resultsdemonstrate that at 9 GHz, the metasurface produces a bifocal effect with focusing efficienciesof 60.1% and 64.3%, respectively, in conjunction with a Bessel beam exhibiting a diffractionfree region of 799 mm. For x-polarization, the full width at half-maximum (FWHM) of thepost-feed Bessel beam is 49.83 mm (1.49 λ). In contrast, under y-polarization, the FWHM ofthe Bessel beam with an off-axis angle of 30° is 47.63mm (1.43 λ). Simulated results suggestthat the proposed metasurface has promising applications in point-to-multipoint or same-pathmulti-target wireless power transmission (WPT) systems.

Analysis Of THz Unit-structured Grating Metasurface Wave Plate

Ji Zhang and Yandong Gong

DOI: 10.1364/AO.537382 Received 23 Jul 2024; Accepted 07 Aug 2024; Posted 09 Aug 2024  View: PDF

Abstract: Conventional grating quarter plates (QWPs) usually utilize the birefringence effect to achieve the modulation of the polarization state of the incident wave, however, the operating bandwidth is narrow. Metasurface is two-dimensional material with periodically aligned structures, which is characterized by thinner volume and larger operating bandwidth. In this paper, it is found that the combination of a conventional grating with a metasurface, which divides the entire conventional grating into multiple sets of unit-structured grating metasurfaces according to the number of grating stripe periods, leads to a certain increase in dispersion bandwidth of the QWP due to the differences in the model patterns formed. By comparing the working bandwidth of the grating metasurface QWP with different stripe periods, it is concluded that the fewer the stripe periods of the grating metasurface QWP, the larger the working bandwidth is obtained at low rotational degrees, and the more the stripe periods are, the larger the working bandwidth can be maintained at high rotational angles. This research has design guidance for the next multilayer rotating ultra-broadband achromatic wave plate.

Efficient ultraviolet beam generation at 294.5 nm by frequency-quadrupling LD-pumped actively Qswitched Nd:YAG/SrWO4 Raman laser

Lu Huang, Xin Wu, Haiyan Li, Zhenshuai Wei, Zhigang Zhao, zhenhua cong, and Zhaojun Liu

DOI: 10.1364/AO.530323 Received 15 May 2024; Accepted 07 Aug 2024; Posted 07 Aug 2024  View: PDF

Abstract: An efficient all-solid-state ultraviolet laser at 294.5 nm isdemonstrated based on the stimulated Raman scatteringand two stages of second-harmonic generation. Withthree-mirror cavity, a 2.63-W laser at 589.6 nm with apulse width of ~8.5 ns and a pulse repetition frequency of20 kHz is obtained. Employing a BBO crystal as thefrequency-doubled medium, a 332-mW UV beam at 294.5nm with a pulse width of ~5.8 ns is obtained under anincident pump power of 14.12 W, the correspondingconversion efficiency is 2.4% from 808 nm to 294.5 nm.

Machine Learning-Driven Optimization of Photonic Crystal Structures for Superior Optical NOR Gate Performance

Fariborz Parandin, Pouya Karami, and Alireza Mohammadi

DOI: 10.1364/AO.529142 Received 09 May 2024; Accepted 07 Aug 2024; Posted 08 Aug 2024  View: PDF

Abstract: In this study, we employ a two-dimensional photonic crystal structure to design aNOR logic gate, utilizing dielectric rods in air. The compact size and simplicity of design makethis optical gate particularly suitable for integration into photonic integrated circuits. Tooptimize the optical NOR gate design and achieve superior results, we leverage machinelearning techniques, specifically XGBoost and RandomForestRegressor. By fine-tuning theradii of defect rods within the photonic crystal lattice, we maximize output power and ensureoptimal gate functionality across various input scenarios. Through extensive simulations andcomparative analyses, we showcase the effectiveness of our approach in accurately predictingoptimal rod radii and enhancing NOR gate performance. Notably, our design utilizes only twodefect rods, highlighting the structure's efficiency. Moreover, alongside the simplicity of ourproposed design, it boasts high output power for logical 1 and low power for logical 0. Thisfeature contributes to minimized errors in logical output detection, further underscoring thepracticality and efficacy of our approach.

Characteristics of ion beam in figuring process on optical ultra-low expansion glass surface

Hsing-Yu Wu, Li-Siang Shen, Shao-Rong Huang, Wen-Wei Lin, Li-Jen Hsiao, Ching-Ling Cheng, Guoyu Yu, Yung-shin Sun, and Jin-Cherng Hsu

DOI: 10.1364/AO.530314 Received 15 May 2024; Accepted 07 Aug 2024; Posted 08 Aug 2024  View: PDF

Abstract: In the study, an ion source figured out the surface of a glass-ceramic material with an ultra-low thermalexpansion coefficient for space optical elements. The investigation of the single-point, line, and square figuringpatterns assessed the detailed characteristics of the ion beam. At a fixed ion beam current and processing time, a beamvoltage of 600 V led to the greatest removal depth with the narrowest full width at half maximum (FWHM). Thesurface roughness under different beam voltages was also examined and discussed. Line figuring with an ion beamvoltage of 600 V and a one-dimensional sample moving speed of 0.25 mm/s exhibited a maximum depth removal rateof 19.71 nm/min after 15 times polishing. Two-dimensional square figuring was performed to polish a plane mirrorwith a diameter of 60 mm, and it successfully reduced its surface's peak-to-valley value to 18 nm due to the meltingheat phenomenon of the glass-ceramic material in ion beam figuring (IBF).

Two-photon polymerization based fabrication of millimeter-sized precision Fresnel optics

Jan Marx, Felix Behlau, Damian Haske, Cemal Esen, and Andreas Ostendorf

DOI: 10.1364/AO.531069 Received 30 May 2024; Accepted 07 Aug 2024; Posted 08 Aug 2024  View: PDF

Abstract: Two photon polymerization (2PP) is known to be the most precise and highestresolution additive manufacturing process for printing optics, but its applicability is restrictedto a few applications due to the limited size of printable objects and low throughput. Thepresented work is intended to demonstrate the performance of printing millimeter-scale opticsby implementing appropriate stitching methods into a setup that combines a Galvo scanner andtranslational axes. In this work, specifically, Fresnel axicons with a diameter of 3.5 mm aremanufactured by 2PP to substantiate the applicability of the process. Manufacturing Fresneloptics instead of volumetric optics allows for attaining acceptable process times with durationsof tens of hours highlighting the appeal of 2PP for rapid prototyping in optics. The suitabilityof the Fresnel axicons for beam shaping is confirmed through illumination with a laser beam.The resulting ring-shaped intensity distribution in the far field behind the Fresnel axicon iscaptured using a beam profiler. Furthermore, the influence of different stitching parameters onthe resulting intensity distribution is investigated. The experimental results are validated bysimulations, where the intensity distribution in the far field behind an axicon was calculatedby Fourier transformation. Simulations were carried out to discuss the effect of manufacturingerrors on the far field intensity distribution.

Planar near-field measurements of specular and diffuse reflection of millimeter-wave absorbers

Fumiya Miura, Hayato Takakura, Yutaro Sekimoto, Junji Inatani, Frederick Matsuda, Shugo Oguri, and Shogo Nakamura

DOI: 10.1364/AO.531654 Received 03 Jun 2024; Accepted 07 Aug 2024; Posted 08 Aug 2024  View: PDF

Abstract: Mitigating the far sidelobes of a wide field-of-view telescope is one of the critical issues for polarization observation of the cosmic microwave background. Since evensmall reflections of stray light at the millimeter-waveabsorbers inside the telescope may create nonnegligiblefar sidelobes, we have developed a method to measurethe reflectance of millimeter-wave absorbers, includingdiffuse reflections. By applying the planar near-fieldmeasurement method to the absorbers, we have enabledtwo-dimensional diffuse-reflection measurements, inaddition to characterizing specular reflection. We havemeasured the reflectance of five samples (TK RAM Largeand Small Tiles and Eccosorb AN-72, HR-10, and LS-22)at two angles of incidence in the frequency range from70 GHz to 110 GHz. Compared with conventional hornto-horn measurements, we obtained a consistent specular reflectance with a higher precision, less affected bystanding waves. We have demonstrated that the angularresponse and diffuse-to-specular reflectance ratio differ among various materials. The measurements alsoimply that some absorbers may affect the polarizationdirection when reflecting the incident waves.

Research on parallel RSA encryption algorithm based on ternary optical computer

kai song, Huanyu Hu, liping yan, Xinjun Hou, and Jingyang Wei

DOI: 10.1364/AO.536463 Received 11 Jul 2024; Accepted 06 Aug 2024; Posted 07 Aug 2024  View: PDF

Abstract: The RSA algorithm remains one of the most influential and extensively used public-key encryption algorithms in today's cryptographic domain. However, the traditional RSA encryption algorithm has several drawbacks, including slow computational speed, high computational cost, and substantial space requirements in practical applications. Consequently, this study amalgamates the characteristics of ternary optical computer (TOC), including high parallelism, multi-digit precision, and low energy consumption, to research and propose a dual-channel transmission encryption strategy and a parallel rapid RSA encryption algorithm. Leveraging the dual-rotary optical structure of TOC and the simplest Most Significant Digit (MSD) encoding, we implement a fundamental encryption strategy based on TOC. Concurrently, we harness the high parallelism attributes of TOC to design large-number parallel modular exponentiation modules, enabling the generation of large prime numbers and efficient computation of large integer modular exponentiation operations. This innovation surmounts the drawbacks of traditional RSA algorithms and further enhances the efficiency of the encryption algorithm. Through resource and time analysis of the algorithm, as well as validation through experimental cases, it is evident that the TOC-based parallel rapid RSA encryption algorithm exhibits excellent computational efficiency and time performance. This research optimally exploits TOC's advantages in handling high parallelism and extensive computational tasks.

Refraction Displacement Pulse Sequence Combination Based On Fast Steering Mirror Stabilization System

Yuxuan Zhang, Jian Xu, Keling Gong, lin zhang, Changzhi Sun, Zihao Wang, Yingjie Lan, Xuekun Zhang, Yong Bo, and qinjun peng

DOI: 10.1364/AO.533033 Received 25 Jun 2024; Accepted 06 Aug 2024; Posted 06 Aug 2024  View: PDF

Abstract: In this paper, a fast steering mirror (FSM) stabilizationsystem is proposed for a refraction displacement pulsesequence beam combining (PSBC) technique. The FSMsystem can effectively suppress pointing jitter in the PSBCand achieve high beam quality laser output. A proof-ofprinciple experiment on the PSBC with FSM is performedwith three ~100 W pulsed beams. The experimentalresults indicate that a combined output power of 302.5 Wis achieved, corresponding to a high combining efficiencyof 98.7%. Meanwhile, an excellent pointing stability withroot mean square (RMS) pointing jitter = 4.2 μrad isconfirmed with a beam quality β of 2.

X-ray reflective coatings made of Pt, Al2O3/Pt, and Al2O3/Ni/Pt produced by atomic layer deposition

David Windt, Huazhi Li, Dmitry Gorelikov, Eric Gullikson, Christian Gollwitzer, Michael Krumrey, and Christian Laubis

DOI: 10.1364/AO.535173 Received 09 Jul 2024; Accepted 05 Aug 2024; Posted 06 Aug 2024  View: PDF

Abstract: The X-ray reflectance of Pt-based coatings deposited by atomic layer deposition (ALD) has been measured, in support of assessing the feasibility of using this deposition method for the production of X-ray mirror coatings that can achieve high X-ray reflectance without causing unacceptably large degradation of mirror figure as a result of coating stress-driven substrate deformation. Specifically, reflectance measurements of single-layer Pt, Al2O3/Pt bilayer, and Al2O3/Ni/Pt trilayer coatings grown by ALD on flat Si substrates were made using synchrotron radiation at X-ray energies in the range from 0.35 to 10 keV, revealing that the reflectance of the bilayers and trilayers is superior to that of single-layer sputtered Ir below 3.5 keV. Single-layer Pt and Al2O3/Pt bilayer coatings produced using thermal ALD were also deposited onto both the front and back surfaces of thin, figured, sub-arcsecond-quality X-ray telescope mirror segments made of polished, single-crystal Si, without discernible degradation of surface figure. These results, along with the successful implementation of batch-coating of two such mirrors simultaneously with high-reflectance coatings grown by thermal ALD, demonstrate the viability of employing stress-balanced, double-sided ALD coatings to mitigate substrate deformation resulting from film stress in high-reflectance coatings. This approach may thus enable the mass production of high-performance, sub-arcsecond X-ray telescope mirrors.

Optimizing LCD structures to mitigate carbon emissions based on root-mean-square values

Chia Hung Yeh and Wei Min Chen

DOI: 10.1364/AO.533761 Received 27 Jun 2024; Accepted 05 Aug 2024; Posted 05 Aug 2024  View: PDF

Abstract: Taiwan is among the leading global producers of display panels, with a GDP ashigh as 8%. In light of the European Union's ambitious European Green Deal, whichaims for a 55% reduction in carbon emissions by 2030 and carbon neutrality by 2050,the advancement of low-carbon emission panel technology is becoming an inevitabletrend. Liquid-crystal display (LCD) technology, known for its non-self-emitting lightdisplay, is faced with a significant challenge—the utilization of polarizers and colorfilters results in a staggering 90% loss of luminance. Therefore, the need to maintain orenhance brightness is crucial for mitigating the carbon footprint. The transition fromconventional light-emitting diodes (LEDs) to mini LEDs has significantly reducedcarbon emissions. However, the heat generated by tens of thousands of mini LEDsposes a new challenge, increasing carbon emissions and raising concerns regarding theenvironmental sustainability. This study focuses on improving the LCD structure toreduce carbon emissions using root-mean-square (RMS) values, with a 32" LCD as anexample. Through simulations using ANSYS SPEOS optical software, we analyzed theoptimal alignment of the mini LED pitch and optimal combination of the height andangle of the brightness enhancement film to achieve an RMS value close to one, whichis the target. The most successful outcomes of this analysis include reducing the numberof mini LEDs by 224 pieces, resulting in a 51.02% reduction in carbon emissions whilemaintaining panel uniformity. This achievement highlights our commitment toenvironmental protection and sustainable development.

Multifocal array camera system design

Shengtai Zhu, Jose Sasian, and David Brady

DOI: 10.1364/AO.528972 Received 06 May 2024; Accepted 05 Aug 2024; Posted 06 Aug 2024  View: PDF

Abstract: Traditional cameras rely on focusing mechanisms for high-performance imagingover a large depth range. However, focusing mechanisms are usually complicated, bulky, andcostly. Here we consider multifocal array cameras that eliminate the need for focusingmechanisms. In the system, lenses with different focal lengths cover different depth ranges, andfocusing is achieved digitally by selecting images from the designated channels. Eliminatingthe need to focus enables simple high-performance designs for individual cameras. Variouslens design techniques, including the selection of design forms, aberration correction,athermalization, and lens desensitizing, are discussed in detail.

Surface error effect on reflectivity and focused spot of EUV tubular mirror machined by ultra-precision diamond turning

Shan Wu, Jinshi Wang, Huaiyu Cui, Yongpeng Zhao, and Fengzhou Fang

DOI: 10.1364/AO.529298 Received 06 May 2024; Accepted 05 Aug 2024; Posted 06 Aug 2024  View: PDF

Abstract: Grazing-incidence tubular mirrors, which provide high reflectivity and significant demagnification of the meridian and sagittal plane through a single reflection, are important optical elements in extreme ultraviolet focusing systems. Surface errors induced by the manufacturing process have a vital impact on optical performance. In this paper, a tubular focusing mirror is directly fabricated via ultra-precision diamond turning. According to ray tracing and Rayleigh-Rice vector perturbation theory, a surface error model is established based on the measurement data from different spatial frequency ranges. The effects of figure error and roughness on the reflectivity and the focused spot are studied in detail. The results reveal that these surface errors cause a decrease in reflectivity from 88.9% to 83.2%, along with a significant increase in the root mean square spot radius, rising from 63.9 μm to 138.3 μm. This study also provides a method to bridge the machined surface geometry to the optical functionality.

A Dark-Field Surface Defects Detection Method for Multi-Surface-Shape Large Aperture Optical Components

Shiwei guo, Shiling wang, Shaowen Wang, Lan Wu, and Dong Liu

DOI: 10.1364/AO.531320 Received 30 May 2024; Accepted 04 Aug 2024; Posted 09 Aug 2024  View: PDF

Abstract: In large-scale high-power optical systems such as inertial confinement fusion systems, the design of various optical components tends towards being larger and more complex. In this regard, surface defects detection, as a fundamental aspect of optical component quality assessment, is faced new challenges, namely the ability to cope with multi complex surface shapes and large detection apertures. Meanwhile, the accuracy level of detection does not decrease with an increase in detection aperture size. Defects to be detected exhibit characteristics such as small scale, low density, and wide distribution range. Therefore, it is required that the detection system maintains compatibility with multi surface shapes while balancing detection efficiency and accuracy. Against this background, the surface defects detection technology with high compatibility is explored in this paper. The illumination system of the dark-field imaging system and a generalized scanning path search strategy is proposed. Under the condition of ensuring a detection sensitivity of 0.5μm, surface defects detection for various types of optical components with apertures several hundred times larger than the detection field of view is achieved.

A calibration-free scheme for frequency response measurement of Mach-Zehnder modulator with low-frequency detection

Liang Xie, mingqi jiao, lei li, Yuxuan Jiang, and Congbiao Lei

DOI: 10.1364/AO.533670 Received 21 Jun 2024; Accepted 03 Aug 2024; Posted 05 Aug 2024  View: PDF

Abstract: This paper presents a novel calibration-free scheme for measuring the frequency response of Mach-Zehnder modulation(MZM) using low-frequency detection. An auxiliary MZM1 modulated by a MHz-level electrical signal f1 is utilized togenerate a double sideband optical signal, which is subsequently directed into the device under test (MZM2). The MZM2is biased at its minimum point and driven by a frequency-swept microwave signal fm. After photo-electric converting, afixed low-frequency electrical signal fL carrying the frequency response information of MZM2 is generated. By sweepingfm while extracting the amplitude of fL, the frequency response of the MZM2 free from the response of photodetector (PD)is thus determined. In the experiment, the frequency response of a commercial MZM is characterized in the frequencyrange from 0.1 GHz to 20 GHz with a resolution of 50 MHz. The measurement result is consistent with the vector networkanalyzer swept method.In addition, the new method eliminates errors introduced by the PD and reduces the requirementfor high-bandwidth PD.

Study of Dual-Window Polarization Filtering Characteristics of Rectangular Photonic Crystal Fibers

Zhijun Gao, Huan Ge, guangyuan si, and Yu Ying

DOI: 10.1364/AO.524281 Received 20 Mar 2024; Accepted 02 Aug 2024; Posted 05 Aug 2024  View: PDF

Abstract: This paper presents a photonic crystal fiber (PCF) polarization filter with asquare array arrangement of gold film fillings, allowing for filtering at dual wavelengths.The paper analyzes the dispersion characteristics and loss properties of this structure andoptimizes the structural parameters through adjustments to achieve the best performance.At 1310 nm, the confinement losses of x and y polarization fundamental modes are 903.54dB/cm and 30.51 dB/cm, respectively; at 1640 nm, the confinement losses of y and xpolarization fundamental modes are 479.02 dB/cm and 88.72 dB/cm, respectively. Thecorresponding filtering bandwidths are 390 nm and 350 nm, while the full width halfmaximum (FWHM) is 59.56 nm, indicating excellent selectivity and resolution of the filter.The performance metrics, such as confinement loss, extinction ratios, and bandwidth, arecompared in the paper with those reported for other filters. Additionally, the study alsoanalyzed the filter's performance under varying manufacturing tolerances of gold filmthickness and air hole diameter by 5%, revealing that the filter's performance remains stableand feasible even in the presence of errors.

Theoretical Study of Electrochemically Controlled Polymer Nanoantenna for Optical Switch

Kaili Kuang, qiao Wang, Fangjin Chang, Yutong Yang, Han Chu, and Wei Peng

DOI: 10.1364/AO.530334 Received 15 May 2024; Accepted 02 Aug 2024; Posted 05 Aug 2024  View: PDF

Abstract: Conventional metallic nanoantenna allows the control of light at the nanoscale, buttheir untunable structural setting and material property limit the optical modulation ofnanoantenna. Studying the methods for dynamical control and modulation of light have becomea hot spot in developing and applying of nanooptics. Herein, we propose a bowtie polymer poly(3,4-ethylenedioxythiophene:sulfate) (PEDOT:Sulf) nanoantenna, which enables dynamicalcontrol of the optical responses by electrochemical modulating the plasmonic (oxidated) anddielectric (reduced) states of polymers. The switch effect of nanoantenna is related to theelectric polar mode in the nanoantenna. In addition, we also explore the dependences of theoptical response for the nanoantenna on structural parameters in detail. The tunable responseof nanoantenna has promising applications in optical switch and encoding in informationtransmission.

Beam attenuation coefficient for different water turbidity

Chiara Lodovisi, Fabrizio Gerardi, claudio moriconi, and Silvello Betti

DOI: 10.1364/AO.528477 Received 01 May 2024; Accepted 01 Aug 2024; Posted 01 Aug 2024  View: PDF

Abstract: Interest in underwater optical communications has grown in recent years. A key aspect for the development of such systems is the modeling of light signal propagation in turbid water. In this paper we present an experimental estimation of the light beamattenuation coefficient by varying the turbid water conditions with pollutants and also considering sea and lake water.The estimation of the beam attenuation coefficient 𝑐 is based on laboratory measurements of the optical signal-to-noise ratio (SNR) for underwater transmissions and an analytical model of 𝑐 as a function of SNR. To assess the reliability of the estimation procedure, 𝑐 has been estimated in the case of clear water and the value obtained is very close to that reported in many literature studies. Next, 𝑐 has been estimated for different water conditions. In particular, the results show that the value of 𝑐 for polluted waters varies between 2.875 𝑚−1 and 15.675 𝑚−1. In addition, the values of 𝑐 for lake and clear sea water are 0.6 𝑚−1 and 0.9 𝑚−1, respectively.

Assembly-induced nonuniform deformation prediction and control method for circular flange connectors with spacers in optical lenses support structure

Long Xu, Yong-Chen Pei, Dongping Wang, and Yangyang Hua

DOI: 10.1364/AO.532791 Received 13 Jun 2024; Accepted 01 Aug 2024; Posted 01 Aug 2024  View: PDF

Abstract: Widely utilized in engineering, circular flange connections are typically secured by multiple bolts, but always resulting innonuniform deformations that significantly impact system shape and position accuracies. Numerous scholars havestudied the deformation characteristics under various structures, external loads, bolt preloads and tightening sequencesin classical rough mechanical systems, but there is a lack of research regarding a high-precision optical system. In opticalsystems, nonuniform deformation of the support structure can be transmitted to the lens, causing astigmatic aberrationsand affecting imaging accuracy. In the optical lenses support structure as a circular flange connector, spacers need to beintroduced to adjust the gap between two parts for controlling the optical path. These spacers tend to be more flexiblethan the support structures, thereby significantly affecting assembly-induced nonuniform deformations. However, theinfluence of spacers had been overlooked in previous works, needing to be investigated. In this paper, the effects of spacerparameters and bolt tightening sequences on the assembly-induced nonuniform deformation are investigated by thefinite element method, which is verified experimentally, and an empirical formula is proposed to predict the nonuniformassembly-induced deformation based on the FEM results. According to the prediction results, a method for control theassembly-induced nonuniform deformation by optimizing the bolt preload distribution is proposed. The influence rulescan guide the optimization of spacers and bolt tightening process. The prediction and control method can effectivelypredict and reduce the assembly-induced nonuniform deformation of the circular flange with spacer, reducing theaberration caused by assembly and improving the accuracy of high-precision optical systems.

Tailoring of abrupt autofocusing vortex beams using phase mask

Sunil Vyas and Yuan Luo

DOI: 10.1364/AO.527601 Received 19 Apr 2024; Accepted 01 Aug 2024; Posted 02 Aug 2024  View: PDF

Abstract: Vortex beams, characterized by their helical phase fronts and orbital angular momentum, havegenerated significant interest due to their unique properties. Combining these beams withabrupt autofocusing (AAF) characteristics, which exhibit self-healing and shape transformationduring propagation, offers promising potential for various applications. In this study, wepropose a method to generate AAF vortex beams using a phase-only mask. Our approachinvolves a cubic chirp-modulated axicon phase superimposed with a spiral phase distribution.Through numerical simulations, we investigate the formation and propagation dynamics ofthese beams, exploring the influence of mask parameters on beam characteristics. The pseudo Bessel beam produced at the focal plane by the AAF vortex beam generates a higher-orderBessel beam characterized by helical phase fronts. Our results demonstrate the generation ofAAF vortex beams with well-defined fractional charges and composite vortex structures. Thesefindings contribute to a deeper understanding of AAF vortex beam behavior and lay thegroundwork for their practical implementation in diverse fields.

Numerical study of titanium film ablation under different ultrafast laser parameters: a molecular dynamics simulation combined with two-temperature model

Longchao Cao, Juntao Wang, Wenxing Hu, Congyi Wu, Sheng Liu, Libin Zhang, and Zhen Wang

DOI: 10.1364/AO.531133 Received 28 May 2024; Accepted 31 Jul 2024; Posted 02 Aug 2024  View: PDF

Abstract: To study the ablation mechanism of titanium (Ti) film under ultrafast laser, theirradiation process of Ti film under various pulse widths, energy densities, andwavelengths is studied by molecular dynamics combined with a two-temperature model(MD-TTM). The temperature distribution of Ti film under ultrafast laser irradiation issolved based on TTM and the ablation phenomenon is explored through MD simulation.It is found that the energy density and wavelength have a more significant impact onthe ablation than pulse width. The shorter the laser wavelength, the smaller thepenetration depth and the more obvious the ablation phenomenon. The higher laserenergy density and shorter wavelength result in higher irradiation temperature of the Tifilm, wherein the ablation phenomenon becomes more pronounced. Moreover, thestress distribution of Ti film after ultrafast laser irradiation is investigated, it can befound that the instantaneous laser irradiation induces compressive stress on the entireTi film. The stress within the non-penetration layer is significantly higher than thatwithin the penetration layer of the Ti film, and stress mutations are mainly concentratedat the interface between the penetration and non-penetration layer of Ti film.Furthermore, the pulse width has little effect on the stress of the Ti film in thepenetration layer while larger energy density and shorter wavelength lead to fasterstress release.

Quadrature demodulation with synchronous difference for broadband source-driven resonant fiber-optic gyroscopes

yuxin Wang, Binjie Li, shuang Liu, Junyi Hu, and Huilian Ma

DOI: 10.1364/AO.536617 Received 15 Jul 2024; Accepted 31 Jul 2024; Posted 31 Jul 2024  View: PDF

Abstract: A broadband source-driven resonant fiber-optic gyroscope (RFOG) has recently been proposed as a means of achieving navigation-gradeperformance in a 100-meter-long fiber-optic ring resonator with a simple optical structure and signal processing. In this paper, a mathematicalmodel of sinusoidal modulation and synchronous demodulation is developed to analyze the effect of relative intensity noise of the broadbandlight source on gyro performance, so as to obtain the optimal modulation index to minimize the angular random walk. On this basis, aquadrature demodulation synchronous difference scheme is introduced for the broadband source-driven RFOG, which further improves thebias stability of the gyroscope by utilizing its common-mode rejection. Finally, an angle random walk of 0.0026/h1/2 and a bias instability of0.0051/h were demonstrated by using a fiber-optic ring resonator with a length of 109 m and a mean diameter of 7.6 cm.

Optical Computing at the Subwavelength Scale: A Multifunctional MIM Plasmonic Logic Gate

Mohammad Ashraful Haque, Rummanur Rahad, and Md. Omar Faruque

DOI: 10.1364/AO.527662 Received 23 Apr 2024; Accepted 30 Jul 2024; Posted 30 Jul 2024  View: PDF

Abstract: Plasmonic logic gates are important components in integrated photonics. They are essential for high-speed boolean computations and data transmission. For this purpose, an all-optical ultra-compact plasmonic logic gate is proposed in this paper. The design uses the Metal-insulator-metal (MIM) configuration and the propagation of surface plasmon polaritons (SPPs). The structure comprises three rectangular input slots coupled to the output slot through a rectangular resonator positioned on a gold (Au) surface with a footprint of 1000 nm $\times$ 800 nm. The logic gate is numerically investigated using the finite element method (FEM) analysis. It has been demonstrated that the proposed design can operate as OR, XOR, NOT, and AND gates and their transmission spectra for different input states are analyzed. This novel solution excels in high contrast ratio (CR) values of 45.34 dB (OR), 18.29 dB (XOR), 18.29 dB (NOT), and 7.26 dB (AND). The logic gate works at the visible spectrum and the resonant wavelengths are 821.21 nm (OR), 863. nm (XOR), 814.71 (NOT), and 787.69 nm (AND). The introduction of this plasmonic logic gate not only expands the repertoire of integrated photonics components but also promises breakthroughs in high-speed data processing and communication technologies, positioning it as a crucial advancement in the field of nanophotonics.

Design and fabrication of Fresnel zone plate with an enhanced depth of focus

HIEU TRAN DOAN TRUNG, HAI LINH VU NGUYEN, ATAR MUNNIBEE, Young-Jin Kim, Young-Sik Ghim, and Hyug-Gyo Rhee

DOI: 10.1364/AO.531033 Received 30 May 2024; Accepted 30 Jul 2024; Posted 31 Jul 2024  View: PDF

Abstract: A Fresnel zone plate (EFZP) with an extended depth of focus can maintain focused monochromaticlight at different distances compared to a general Fresnel zone plate (FZP). The focal distances are determined bydividing the zone plate into multiple areas based on the desired order. The EFZP has potential applications invarious research fields such as microscopy, direct laser lithography, and optical coherence tomography. However,manufacturing an EFZP is challenging due to the high precision requirements and difficulties associated with thecalculation and simulation processes. In this research, a complete process is presented to design, simulate, andfabricate an EFZP using Fourier optics design, simulations, and a direct laser lithographic machine. The resultingEFZP has an increased depth of focus of about nine times compared to a general Fresnel zone plate with similarparameters, while maintaining the focal spot diameter. The performance of this EFZP is evaluated through opticalverification and mathematical simulation methods.

Power Spectral Density Analysis of Midspatial Frequency Error in the BK7 Glass Lenses Polishing Process

Yu-Hsiang Lo, Jyun-Ting Lin, YU-ZHEN MAO, HSUAN-CHUN CHEN, and Chun-Wei Liu

DOI: 10.1364/AO.531620 Received 31 May 2024; Accepted 30 Jul 2024; Posted 31 Jul 2024  View: PDF

Abstract: This study reduced mid-spatial-frequency (MSF) errors in optical componentpolishing by using subaperture techniques such as bonnet polishing. MSF errors can degradeoptical imaging quality by causing light scattering and reducing system resolution. Byoptimizing a spiral path and incorporating machine learning techniques, such as support vectorregression (SVR) and Gaussian process regression (GPR), the SVR and GPR models achievedan R2 value exceeding 85%. The optimized root mean square error (RMSE) of the powerspectral density (PSD) value was 0.93 × 10−3 μm^3, with the maximum and minimum errorreductions being 97.0% and 10.4%, respectively. Thus, the optical surface quality improvedsubstantially, indicating the effectiveness of optimization techniques in reducing MSF error.

Research on online detection technology of triangular-blade tool grinding precision based on machine vision

Weijun Hong, Huawei Ji, Changhao Wang, and Xiaoping Hu

DOI: 10.1364/AO.531927 Received 04 Jun 2024; Accepted 30 Jul 2024; Posted 31 Jul 2024  View: PDF

Abstract: To address the problems of repeat positioning accuracy and secondary clampingcaused by triangular-blade tool during grinding, this paper proposes an online detection methodfor the machining accuracy of triangular-blade tool based on machine vision. The methodutilizes a weighted average approach for grayscale processing of the original image and anadaptive median filtering algorithm for filtering and noise reduction. The processed image isthen binarized. The Canny and Zernike moment edge detection algorithms are utilized forpixel-level and sub-pixel-level edge positioning. A curvature-based feature extraction methodis proposed to complete image stitching. Measurement software is designed and developed onthe MATLAB app designer platform. Experimental results show that the relative error in toolgrinding length is within 0.094%, the average error in cutting edge width is 1.105%, the relativeerror in thickness is 5.065%, and the relative error in symmetry is 6.044%. The accuracy of theproposed method is confirmed through a comparison between image measurement andmicroscope measurement.

Harnessing Tin Phthalocyanine for Ultrafast Modelocking in Erbium-doped fiber Laser

Salam Azooz, Sameer Salam, ABDULKADIR MUKHTAR DIBLAWE, Ahmad Razif Muhammad, Bilal Nizamani, and Sulaiman Wadi Harun

DOI: 10.1364/AO.530956 Received 30 May 2024; Accepted 29 Jul 2024; Posted 29 Jul 2024  View: PDF

Abstract: We present the first demonstration, to our knowledge, of a mode-locked erbium-doped fiber laser (EDFL) employing tinphthalocyanines (SnPc) as a saturable absorber (SA). The investigated SA exhibits a notable modulation depth of 18.6%,fabricated via a simple, cost-effective method, wherein the SnPc compound is embedded into a polyvinyl alcohol (PVA)film. Integration of this thin film into the EDFL cavity facilitates the generation of output pulses with a repetition rate of0.96 MHz and a pulse duration of 2.68 ps. The frequency spectrum showcases a signal-to-noise ratio of up to 73.2 dB,affirming the stability of the mode-locking operation. Operating at a wavelength of 1531.7 nm, this picosecond pulse trainholds significant promise for diverse applications, including high-precision optical metrology, frequency-combgeneration, and broadband absorption spectroscopy.

Photometric Stereo Multi-information Fusion Unsupervised Anomaly Detection Algorithm

Lan Jianmin and Shi Jinjin

DOI: 10.1364/AO.524199 Received 01 Apr 2024; Accepted 29 Jul 2024; Posted 29 Jul 2024  View: PDF

Abstract: Due to different materials, the product surface is susceptible to light, shadow,reflection, and other factors, coupled with the appearance of defects of various shapes and types,as well as dust, impurities, and other interfering influences, resulting in normal and abnormalsamples difficult to distinguish, is a common problem in the field of defect detection. Giventhis, this paper proposes an end-to-end photometric stereo multi-information fusionunsupervised anomaly detection model. First, the photometric stereo feature generator is usedto obtain normal, reflectance, depth, and other information to reconstruct the 3D topographicdetails of the object's surface. Second, a multi-scale channel attention mechanism is constructedto fully use the feature associations of different layers of the backbone network, and the limitedfeature information is used to enhance the defect characterization ability. Finally, the originalimage is fused with normal and depth features to find the feature variability between defectsand defects, as well as between defects and background, and the feature differences betweenthe source and clone networks are utilized to achieve multi-scale detection and improvedetection accuracy. In this paper, the model performance is verified on the PSAD dataset. Theexperimental results show that the algorithm in this paper has higher detection accuracycompared with other algorithms. Among them, the multi-scale attention mechanism and multiinformation fusion input improve the detection accuracy by 2.56% and 1.57%, respectively. Inaddition, the ablation experiments further validate the effectiveness of the detection algorithmin this paper.

Structure Factors Design of Liquid Crystal Beam Steering Device for Augmented Reality Applications

Yu-Min Chen, Chung-Jen Ou, Hung-Ta Chien, Jui-Yi Wu, Ming-Wei Tsai, Chien-Chih Chen, and Huang-Ming Chen

DOI: 10.1364/AO.530407 Received 20 May 2024; Accepted 29 Jul 2024; Posted 29 Jul 2024  View: PDF

Abstract: The applications of AR and VR devices have beenincreasingly important in our daily life. There are somedisadvantages remaining to be improved for real timeapplication. In this paper, we demonstrated the design ofthe experiment based on the Taguchi method targeting abeam steering liquid crystal device possessed 6 degreesteering angle with fast switch (>60 Hz) ability for viewingangle expansion in AR/VR device. Approach of the beststructure design was suggested from the recall table thatconcluding the optical phenomenon affected by theselected parameters from simulation. The resultingdesign rule was tape-out to prepare the pattern ITO glass.The beam steering device was assembled according thesuggested cell gap. The device evaluation showed a 6.1degree steering angle as predicted. The response time wasmeasured as 10.5 ms which is able to be driven well above60 Hz.

Regularity of bifurcation in self-mixing laser diode

Cholhyon Kim, Gun-Jong Ko, Hyok-Chol Kim, and Kwang-Myong Ho

DOI: 10.1364/AO.530887 Received 29 May 2024; Accepted 29 Jul 2024; Posted 29 Jul 2024  View: PDF

Abstract: To acquire stable self-mixing signals in self-mixing interferometry is the primary requirement for themeasurement. This paper finds that “strange” self-mixing signals which has an evil effect on the self-mixinginterferometry are related to the injection current of the semiconductor laser based on the rate equation of thesemiconductor laser proposes the method of guaranteeing stable self-mixing interferometry. The paper will be amilestone which is of a very vital significance in consolidating the theoretical foundation of self-mixinginterferometry and securing its application.

Interactive zoom display in smartphone-based digital holographic microscope for 3D imaging

Yuki Nagahama

DOI: 10.1364/AO.532972 Received 17 Jun 2024; Accepted 29 Jul 2024; Posted 29 Jul 2024  View: PDF

Abstract: Digital holography has applications in bio-imagingbecause it can simultaneously obtain the amplitude andphase information of a microscopic sample in a singleshot, thus facilitating non-contact, noninvasiveobservation of the 3D shape of transparent objects (phaseobjects, which can be mapped with the phaseinformation,) and moving objects. The combination ofdigital holography and microscopy is called digitalholographic microscopy (DHM). In this study, we proposea smartphone-based DHM system for 3D imaging that iscompact, inexpensive, and capable of observing objects inreal time; this system includes an optical systemcomprising a 3D printer using commercially availableimage sensors and semiconductor lasers; further, anAndroid-based application is used to reconstruct theholograms acquired by this optical system, thus outliningthe amplitude and phase information of the observedobject. Also, by utilizing scalable diffraction calculationmethods and touchscreen interaction, we implementedzoom functionality through pinch-in gestures. The studyresults showed that the DHM system successfully obtainedthe amplitude and phase information of the observedobject via the acquired holograms in an almost real timemanner. Thus, this study showed that it is possible toconstruct a low cost and compact DHM system thatincludes a 3D printer to construct the optical system anda smartphone application to reconstruct the holograms.Furthermore, this smartphone-based DHM system'sability to capture, reconstruct, and display holograms inreal time demonstrates its superiority and novelty overexisting systems. This system is also expected tocontribute to biology fieldwork and pathologicaldiagnosis in remote areas.

Quantitative phase imaging based on transport‐of‐ intensity equation using white‐light diffraction phase microscopy

Weizhe Cheng, Yunpeng Feng, Le Yu, and Haobo Cheng

DOI: 10.1364/AO.531779 Received 05 Jun 2024; Accepted 28 Jul 2024; Posted 29 Jul 2024  View: PDF

Abstract: We present a compact quantitative phase imaging (QPI) system based on the white‐light diffraction phase microscopy(wDPM) configuration. This system is capable of capturing wide‐field digital holograms (DH) under low‐coherenceillumination while maintaining high spatiotemporal sensitivity and stability.Our cost‐effective module is compatible withimaging devices such as the bright‐field microscope, simplifying the QPI process significantly in a label‐free manner.Additionally, itfacilitates a detailed comparison between the wDPM,transport‐of‐intensity equation (TIE) phase retrievalmethods and other QPI methods, serving as a multimodal platform. Moreover, we achieved direct QPI of a single‐shot DHthrough multichannel wavefront reconstruction, acquisition of chromatic aberration, and implementation of the TIEmethod. This approach circumvents the need for cumbersome phase unwrapping (PU) and aberration correctionprocedures typical in wDPM, highlighting the potential of QPI using the proposed wDPM‐TIE method. Furthermore, toaddress the halo effect inherent in wDPM, we reconstructed the reference beam wavefront through TIE and utilized it tomitigate the halo artifacts. Simulation and comparative experimental results affirm the feasibility， accuracy, anddynamic QPI capability of the proposed configuration together with the wDPM‐TIE QPI method in both micro‐optics andbio‐imaging, showcasing nanometer‐level spatial and temporal noise.

Using femtosecond laser pulses to investigate the thickness-dependent nonlinear optical properties of nickel oxide thin films and their potential use as optical limiters

Mona Mustafa, mona ali, Mohamed Abdel-wahab, Wael Tawfik, M. F. Eissa, M.A.k. Elfayoumi, Hany Hamdy, and Tarek Hassan

DOI: 10.1364/AO.532434 Received 07 Jun 2024; Accepted 28 Jul 2024; Posted 29 Jul 2024  View: PDF

Abstract: In this study, the Z-scan technique was used to investigate the nonlinear optical properties of NiO thin filmsof various thicknesses. Direct current (DC) sputtering was used to deposit single-phase NiO thin films withthicknesses of 280, 350, and 470 nm onto a soda lime glass substrate. The film structure was measured usingX-ray diffraction (XRD) and scanning electron microscopy (SEM), while the linear optical properties weremeasured using a UV‒Vis spectrophotometer. NiO thin films were irradiated with 100 fs laser pulses atvarious excitation wavelengths and excitation powers to determine the nonlinear absorption coefficient andnonlinear refractive index. The NiO films were found to have reverse saturable absorption and self-focusingbehavior. As the thickness of the NiO film increases, both the nonlinear absorption coefficient and nonlinearrefractive index decrease. Additionally, the investigation of the optical limitations of NiO thin films revealeda definite association with the thickness of the NiO thin film.

Fabrication of PSCs with light absorption chips utilizing double-metal-cladding waveguide technology

Yutian Liu, Junjie Yang, Yanbin Chen, Qianliu Yin, Rui Shen, Zixiang Dai, Qianyi Jiao, Zhicheng Sui, and Tian Xu

DOI: 10.1364/AO.533580 Received 21 Jun 2024; Accepted 27 Jul 2024; Posted 29 Jul 2024  View: PDF

Abstract: Metal nanoparticles or periodic metal nanostructures exhibit localized surface plasmon resonance (LSPR) effects, widely employed in photovoltaic devices to enhance light absorption. In this study, we used a double-metal-cladding waveguide (DMCW) structure to fabricate hexagonal metal nanostructures on the front side of the Indium tin oxide (ITO) glass, positioned away from the incident light direction. We then prepared perovskite solar cells under various reaction conditions. Analysis results indicate that the metal nanostructure chip excites near-field coupling, generating strong localized fields, and enhances light absorption through the LSPR effect. The perovskite solar cells (PSCs) with the chip structures exhibited a significant increase in short-circuit current density (JSC) and fill factor (FF), accompanied by a decrease in dark current, indicating improved photovoltaic characteristics of the cells. Altering the evaporative deposition time of the silver film and the concentration of the reaction solution led to a 12.79% increase in the power conversion efficiency (PCE) of the PSCs.

Study on Multi-plane Imaging Technology with Constant Imaging Quality

zhai zhongsheng, Xiatian Yu, Zhen Zeng, Yi Zhang, qinghua lv, Da Liu, and Jun Tu

DOI: 10.1364/AO.528431 Received 25 Apr 2024; Accepted 26 Jul 2024; Posted 26 Jul 2024  View: PDF

Abstract: TTo realize three-dimensional microscopic imagingwith high time resolution and high space resolution at thesame time, a multi-plane imaging method with constant axialmulti-plane imaging quality is proposed. The optical theoryto ensure that different axial sections have consistent lateralresolution has been analyzed. In the system, it is proposed tosuperimpose a spatial light modulator with programmableability and wavefront control function on the focal plane ofthe image square of the front group of the infinite tube lengthmicroscope objective, and load a digital multiplexing lenswith multi-focus and multi-diffraction angle to form a newcombined imaging system. The system can clearly image anyaxial section or multiple target planes within a certainimaging range without compensating the imaging aberrationof the axial section, so that each axial section has the sameimaging quality. With the help of the USAF 1951 resolutionchart, it is verified that different axial object planes haveconsistent lateral resolution up to 57.0 lp/mm. For sampleswith different thicknesses, multi-plane layer-by-layerimaging and multi-plane simultaneous imaging experimentswere performed using single-focus lens, multi-focus Fresnellens and digital multiplexing lens phase grayscale images,respectively. Experimental results show that this scheme canachieve some degree of simultaneous multiplanar imagingwith an axial spacing of up to 0.2 mm, which is potentiallyuseful in research areas where samples should not be movedor where relative motion is not desirable.

Algorithm for detecting airborne objects with a thermal infrared camera to ensure a safe operation of laser-optical ground stations

Jakob Steurer, Nils Bartels, Daniel Hampf, Felicitas Niebler, Tristan Meyer, Wolfgang Riede, and Thomas Dekorsy

DOI: 10.1364/AO.529222 Received 06 May 2024; Accepted 26 Jul 2024; Posted 26 Jul 2024  View: PDF

Abstract: Laser-optical ground stations play an important role for satellite laser communication and satellite laser ranging (SLR). The safe operation of lasers in public airspace, which usually requires approval by legal entities, requires reliable, redundant, and independent systems for airborne object detection to avoid a potentially hazardous laser exposition. In this work, we propose an algorithm based on classical image filtering and thresholding to detect aircraft in images taken with a thermal infrared camera. The algorithm is optimized and evaluated with an image dataset acquired with the infrared camera mounted to SLR station miniSLR® located in Stuttgart, Germany. Despite its simplicity and efficiency (7 ms for an image with 640x512 pixels on a standard consumer PCU), we find that the proposed algorithm has a high accuracy, yielding a 99.8 % correct classification of images. Although laser safety systems require several independent aircraft detection methods, the proposed algorithm might be a valuable contribution for companies and institutes with the need to operate lasers in public airspace.

Polarization-filterless polarization-sensitive polarization-multiplexed phase-shifting self-reference digital holography (P4SDH)

Tatsuki Tahara

DOI: 10.1364/AO.521815 Received 20 Feb 2024; Accepted 26 Jul 2024; Posted 26 Jul 2024  View: PDF

Abstract: I propose a phase-shifting self-reference digital holography technique in which both three-dimensional (3D) and polarization information is simultaneously obtained without any polarization filters. A Fourier-transform lens, a polarization beam splitter, and two phase-only spatial light modulators are used to simultaneously generate self-reference holograms with orthogonal polarization directions. 3D and polarization information is multiplexed in the recorded phase-shifted digital holograms and retrieved by applying polarization-selective phase-shifting interferometry and numerical refocusing. The validity of the proposed technique is experimentally demonstrated.

Implementation of atomic layer deposited AZO films in SLM structures

Vera Marinova, Stefan Petrov, NGUYEN HONG MINH CHAU, DIMITRINA PETROVA, BLAGOVEST NAPOLEONOV, VLADIMIRA VIDEVA, Ken Hsu, Dimitre Dimitrov, and Shiuan-Huei Lin

DOI: 10.1364/AO.527610 Received 25 Apr 2024; Accepted 26 Jul 2024; Posted 26 Jul 2024  View: PDF

Abstract: Here, we demonstrate the implementation of transparent conductive Aluminum-doped Zinc Oxide (AZO) thin films deposited on glass substrate (AZO/Glass) by Atomic Layer Deposition (ALD) technique in Liquid Crystal (LC) Spatial Light Modulator (SLM) devices. Structural, optical and electrical properties as well as surface free energy reveal the high quality and uniformity of deposited AZO layers. We present two types of structures that highlight the multifunctional role of AZO thin films in SLM configurations: (i) as transparent conductive layer for assembling regular antiparallel (AP) LC cell and (ii) as transparent conductive layer and alignment layer allowing vertical alignment (VA) in LC display devices. A comparison of the electro-optical parameters such as pre-tilt angle, phase modulation, driving voltage, response time, etc. of both devices are presented and discussed. AZO thin films prove superior performance, indicating a growing demand for the next generation indium tin oxide (ITO)-free technology, including advanced display devices and dynamic flat-panel functionalities.

High Q-factor Fano resonances based on alldielectric metasurface for high-performance refractive index sensing

Tingting Wang, Wenjing Fang, HaoYu Guo, JieLong Pang, Xinye Fan, chuanchuan li, Xin Wei, and Santosh Kumar

DOI: 10.1364/AO.532692 Received 12 Jun 2024; Accepted 26 Jul 2024; Posted 29 Jul 2024  View: PDF

Abstract: This paper proposes a high-performance refractive index sensor based on alldielectric metasurface consisting of four silicon arcs arranged back-to-back on a silicondioxide substrate. A sharp Fano resonance with high-quality factor (Q-factor) in the nearinfrared (NIR) wavelength is innovatively excited by electric quadrupole (EQ) resonanceby varying the size of the inner angle. And electromagnetic field distribution and modeassessment are further demonstrated EQ resonance mode is governed by quasi-bound statesin the continuum (Q-BICs). Additionally, the ability to precisely control Fano resonancepeaks is demonstrated by tuning the geometrical parameters of the structure, which makesthe designed metasurface a promising gas refractive index sensing candidate. The resultsshow that the highest Q-factor, sensitivity (S) and figure of merit (FOM) are 6, 603nm/RIU and 9869 RIU-1, respectively. The proposed structure provides a good applicationprospect for nonlinear optical devices and air refractive index sensors.

Three-dimensional image encryption based on structured light illumination and iterative layer-oriented angular-spectrum algorithm

Yiwen Wang, Yanfeng Su, Lijuan Xue, Zhihan Wang, Ruijie Xue, Wenqi Zhong, Jinsong Li, Zhijian Cai, and wenqiang wan

DOI: 10.1364/AO.524817 Received 27 Mar 2024; Accepted 25 Jul 2024; Posted 30 Jul 2024  View: PDF

Abstract: In this paper, a three-dimensional (3D) image encryption method is proposed based on structured light illuminationand iterative layer-oriented angular-spectrum algorithm, where original 3D plaintext image is encrypted into aphase-only hologram ciphertext (POHC). The structured light is generated by using a structured phase mask (SPM), andthe optical parameters in the SPM are all served as the supplementary keys for increasing the types and quantities ofsecurity keys, expanding the key space and enhancing the level of security. Moreover, the introduction of structuredlight also enhances the invisibility of ciphertext and the concealment of valid information, overcoming an inherentsilhouette problem of POHC calculated by a traditional layer-oriented angular-spectrum algorithm, and the iterativecalculation also suppresses the speckle noise of decrypted 3D image, improving the decryption quality. Numericalsimulations are performed to demonstrate the feasibility of the proposed 3D image encryption method, and thesimulation results show that the proposed method exhibits high feasibility and security as well as strong robustness.

Design and manufacture of a modified freeform Offner spectrometer with 0.6X magnification

Lingling Song, Chen Xinhua, Zhicheng Zhao, jiawang wen, and Weimin Shen

DOI: 10.1364/AO.532169 Received 06 Jun 2024; Accepted 25 Jul 2024; Posted 26 Jul 2024  View: PDF

Abstract: The Offner spectrometer is characterize of lower F/#, excellent imaging quality and smalldistortion, which is beneficial from the symmetry and concentricity. However, its 1:1 magnification imposesa constrain on the design, manufacture and alignment of the foreoptics, especially when small F/#applications. The modified Offner spectrometer is hence proposed, and its design and manufacture areintroduced in this paper. The initial structure parameters of the modified Offner spectrometer are solved withthe wave aberration theory of plane-symmetrical system. The primary and tertiary mirrors use the Zernikepolynomial freeform surfaces to improve the imaging quality during optimization. The components of thedesigned modified Offner spectrometer are fabricated and the spectral performance is measured afteralignment. The measured spectral resolution is 3.91nm, and the maximum smile and keystone are 1.37μmand 1.8μm respectively, which are both less than 10% of spatial and spectral dimension pixel.

A dynamically tunable Fano resonator with high sensitivity in terahertz band

Wen Zhang, Ling Zhong, Junyan Cheng, Yuanmei Xu, Liang Ye, and Xueshi Li

DOI: 10.1364/AO.530960 Received 06 Jun 2024; Accepted 24 Jul 2024; Posted 25 Jul 2024  View: PDF

Abstract: A dynamically tunable Fano resonator device with integrated graphene has been designed. It is capable to address the fixed performance of the conventional sensors based on metal-insulator-metal (MIM) waveguide. The resonant frequency of the Fano resonance can be dynamically tuned over a wide range of frequency by regulating the bias voltage of the graphene for flexible tuning and optimised system performance, while maintaining a very high figure of merit (FOM). These indicate the design has a number of advantages, including ease of fabrication, dynamic tunability, high sensitivity and wide wavelength range.

Diffractive optical elements on non-planar surfaces for the formation of color 3D images

Alexander Goncharsky, Anton Goncharsky, and Svyatoslav Durlevich

DOI: 10.1364/AO.528267 Received 06 May 2024; Accepted 22 Jul 2024; Posted 22 Jul 2024  View: PDF

Abstract: This paper is dedicated to the development of synthesis methods for diffractiveoptical elements (DOE) on non-planar surfaces. To form 3D images, a set of color 2D framesis used, visible to an observer from different observation points. The developed DOEs can becalled a stereogram with a 360-degree view when the DOE is illuminated with white light.Methods are developed for computing the phase function of the DOE and are applicable to awide range of convex surfaces. However, the manufacturing technology used limits this rangeto conical and cylindrical surfaces. The microrelief of the flat DOE is produced using electronbeam lithography. A video recorded using optical elements produced demonstrates thecapabilities of the technologies developed. These DOEs can be used to protect brands againstcounterfeit.

Dynamic response diagnosis of ultrasound field in water utilizing Birefringence-Zeeman Dual-Frequency laser

Junwen Sheng, Ziran Jiang, Shengjie Fu, Zilin Wang, liu fen, Fan Gao, and weixin liu

DOI: 10.1364/AO.529775 Received 10 May 2024; Accepted 19 Jul 2024; Posted 22 Jul 2024  View: PDF

Abstract: Interesting interaction between the laser and the ultrasound field in liquid mediumhave been a issue in optical physics research, attracting a large number of experimental andtheoretical studies.To facilitate the real-time detection of dynamic ultrasonic signals withinliquid environments, experiments involving laser heterodyne and self-mixing interferometrywere employed. In order to achieve the experimental purpose, designing Birefringent-ZeemanDual-Frequency laser for experiments. Through experimental and simulation studies, weelucidated the physical mechanism of ultrasound signals propagation in liquid media and theirmodulatory impact on laser systems. Meanwhile, the ultrasonic signal frequency measured viathe laser self-mixing interferometry approach exhibits an average error of 0.87%, a signalintensity of -14.55 dBm, and the sensitivity is 28.9 dB higher than laser heterodyneinterferometry. These high-precision, high-resolution optical detection methodologies promiseto rectify the shortcomings inherent in traditional ultrasonic detection techniques concerningcalibration.

Astrophotonics - current capabilities and the road ahead

Barnaby Norris, Simon Gross, Sergio Leon-Saval, Christopher Betters, Julia Bryant, QINGSHAN YU, Haobing Wang, Glen Douglass, Elizabeth Arcadi, Ahmed Sanny, Michael Withford, Peter Tuthill, and Joss Bland-Hawthorn

DOI: 10.1364/AO.517018 Received 14 Jan 2024; Accepted 19 Jul 2024; Posted 25 Jul 2024  View: PDF

Abstract: Astrophotonics represents a cutting-edge approach in observational astronomy.This paper explores the significant advancements and potential applications of astrophotonics,highlighting how photonic technologies stand to revolutionise astronomical instrumentation. Keyareas of focus include photonic wavefront sensing and imaging, photonic interferometry andnulling, advanced chip fabrication methods, and the integration of spectroscopy and sensing ontophotonic chips. The role of single-mode fibres in reducing modal noise, and the development ofphotonic integral field units (IFUs) and arrayed waveguide gratings (AWGs) for high-resolution,spatially resolved spectroscopy will be examined. As part of the Sydney regional-focus issue,this review aims to detail some of the current technological achievements in this field as well asto discuss the future trajectory of astrophotonics, underscoring its potential to unlock importantnew astronomical discoveries.

Design and analysis of ultra-wide Angle laser communication optical system

lichao Hu, Yan An, zexiang li, Jianhong Li, Yansong Song, and Keyan Dong

DOI: 10.1364/AO.528343 Received 25 Apr 2024; Accepted 17 Jul 2024; Posted 17 Jul 2024  View: PDF

Abstract: With the development of information networks and laser communication technology, the coverage communication formof inter-satellite network has become crucial. In order to solve the problems of small communication field of view anddifficult integration , an optical system design method for network laser communication is proposed. Based on the ultrawide-angle system, the non-similar imaging principle is used to realize the design of a large field of view omnidirectionaloptical antenna, and the communication link of the antenna is analyzed accordingly. The results show that thecommunication field of view of the antenna can reach 130°, and the beam divergence angle increases from 420 μrad to2000 μrad in this range, which can realize long-distance laser communication with a communication rate of 5Gbps. Thedesign method proposed in this paper provides a new design idea for the development of laser communication opticalantenna, which has great application potential in the field of inter-satellite laser communication networking.

Decontamination of a surgical mask with UV-C irradiation: Analysis of experimental results with optical simulations

Titta Kiiskinen, Oliver Mangs, Jussi Virkajärvi, Farid Elsehrawy, Satu Salo, Arttu Miettinen, Janne Halme, Ali Harlin, and Jukka Ketoja

DOI: 10.1364/AO.528056 Received 23 Apr 2024; Accepted 16 Jul 2024; Posted 17 Jul 2024  View: PDF

Abstract: The suitability of ultraviolet-C (UV-C) irradiation for the decontamination of a surgical face mask was studied by decontamination experiments, carried out using Staphylococcus aureus and MS2 microbes. A moderate dosage level of 0.22 J/cm2 achieved within two minutes led to an over 6 log10 reduction in viable microbe contamination of the inner filtering layer. The underlying reason for this effective decontamination of fibers with small external UV-C dosage was explored with ray-tracing optical simulations, supported by optical measurements on reflection and transmission. The model 3D fiber network was constructed from X-ray tomography images of the layered mask structure consisting of polypropylene fibers. Both simulations and optical measurements indicated that UV light was able to penetrate even the deepest material regions. The simulations show that despite radiation reflection from the outer mask layer, a significant dosage enters the actual filtering layer due to multiple refraction and scattering of UV light from the inner fibers.

ALL OPTICAL GENERATION OF FULL-RANGE SYMMETRY-TUNABLE TRIANGULAR-SHAPED PULSES VIA WAVELENGTH MULTIPLEXING

Li Yin, shuna yang, Xinghua Yang, Yuanyuan Yao, Bo Yang, and Hao Chi

DOI: 10.1364/AO.527468 Received 16 Apr 2024; Accepted 08 Jul 2024; Posted 06 Aug 2024  View: PDF

Abstract: A novel all-optical approach for generating full-range symmetry-tunable triangular-shaped pulses through wavelengthmultiplexing is proposed and experimentally demonstrated. Two light waves with a specified wavelength interval areparallelly injected into two commercial push-pull Mach-Zehnder modulators (MZMs) to carry the baseband radiofrequency (RF) input. A tunable optical delay line (ODL) following by one MZM is utilized to introduce the desired phaseshift. By multiplexing the modulated signals carried on two wavelengths, triangular-shaped pulses can be achieved by theopto-electronic conversion. In this approach, by simply adjusting the DC bias voltages and the delay time offered by ODL,the triangular-shaped pulse with any self-defined symmetrical coefficient can be obtained. A complete theoretical analysison operation principle is presented and verified. The triangular-shaped pulses with full-range tunable symmetricalcoefficients at the repetition rate of 5 GHz are successfully generated. This approach features all-optical architecture,ultra-wide system bandwidth, full-range tunable symmetry (0-100%) and excellent reconfigurability, which are highlydesired for the high-performance triangular-shaped pulse generator.