Pub Date : 2024-09-15DOI: 10.1088/2515-7647/ad68df
Ho-Chun Lin, Zeyu Wang and Chia Wei Hsu
Wavefront shaping can tailor multipath interference to control multiple scattering of waves in complex optical systems. However, full-wave simulations that capture multiple scattering are computationally demanding given the large system size and the large number of input channels. Recently, an ‘augmented partial factorization’ (APF) method was proposed to significantly speed-up such full-wave simulations. In this tutorial, we illustrate how to perform wavefront shaping simulations with the APF method using the open-source frequency-domain electromagnetic scattering solver MESTI. We present the foundational concepts and then walk through four examples: computing the scattering matrix of a slab with random permittivities, open high-transmission channels through disorder, focusing inside disorder with phase conjugation, and reflection matrix computation in a spatial focused-beam basis. The goal is to lower the barrier for researchers to use simulations to explore the rich phenomena enabled by wavefront shaping.
{"title":"Wavefront shaping simulations with augmented partial factorization","authors":"Ho-Chun Lin, Zeyu Wang and Chia Wei Hsu","doi":"10.1088/2515-7647/ad68df","DOIUrl":"https://doi.org/10.1088/2515-7647/ad68df","url":null,"abstract":"Wavefront shaping can tailor multipath interference to control multiple scattering of waves in complex optical systems. However, full-wave simulations that capture multiple scattering are computationally demanding given the large system size and the large number of input channels. Recently, an ‘augmented partial factorization’ (APF) method was proposed to significantly speed-up such full-wave simulations. In this tutorial, we illustrate how to perform wavefront shaping simulations with the APF method using the open-source frequency-domain electromagnetic scattering solver MESTI. We present the foundational concepts and then walk through four examples: computing the scattering matrix of a slab with random permittivities, open high-transmission channels through disorder, focusing inside disorder with phase conjugation, and reflection matrix computation in a spatial focused-beam basis. The goal is to lower the barrier for researchers to use simulations to explore the rich phenomena enabled by wavefront shaping.","PeriodicalId":44008,"journal":{"name":"Journal of Physics-Photonics","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-02DOI: 10.1088/2515-7647/ad6ed4
Henna Farheen, Suraj Joshi, J Christoph Scheytt, Viktor Myroshnychenko, Jens Förstner
Phased arrays are vital in communication systems and have received significant interest in the field of optoelectronics and photonics, enabling a wide range of applications such as LiDAR, holography, and wireless communication. In this work, we present a blazed grating antenna that is optimized to have upward radiation efficiency as high as 80% with a compact footprint of 3.5 µm × 2 µm at an operational wavelength of 1.55 µm. Our numerical investigations demonstrate that this antenna in a 64×64 phased array configuration is capable of producing desired far-field radiation patterns. Additionally, our antenna possesses a low side lobe level of −9.7 dB and a negligible reflection efficiency of under 1%, making it an attractive candidate for integrated optical phased arrays.
{"title":"An efficient compact blazed grating antenna for optical phased arrays","authors":"Henna Farheen, Suraj Joshi, J Christoph Scheytt, Viktor Myroshnychenko, Jens Förstner","doi":"10.1088/2515-7647/ad6ed4","DOIUrl":"https://doi.org/10.1088/2515-7647/ad6ed4","url":null,"abstract":"Phased arrays are vital in communication systems and have received significant interest in the field of optoelectronics and photonics, enabling a wide range of applications such as LiDAR, holography, and wireless communication. In this work, we present a blazed grating antenna that is optimized to have upward radiation efficiency as high as 80% with a compact footprint of 3.5 <italic toggle=\"yes\">µ</italic>m × 2 <italic toggle=\"yes\">µ</italic>m at an operational wavelength of 1.55 <italic toggle=\"yes\">µ</italic>m. Our numerical investigations demonstrate that this antenna in a <inline-formula>\u0000<tex-math><?CDATA $64times64$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mn>64</mml:mn><mml:mo>×</mml:mo><mml:mn>64</mml:mn></mml:mrow></mml:math><inline-graphic xlink:href=\"jpphotonad6ed4ieqn1.gif\"></inline-graphic></inline-formula> phased array configuration is capable of producing desired far-field radiation patterns. Additionally, our antenna possesses a low side lobe level of −9.7 dB and a negligible reflection efficiency of under 1%, making it an attractive candidate for integrated optical phased arrays.","PeriodicalId":44008,"journal":{"name":"Journal of Physics-Photonics","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-27DOI: 10.1088/2515-7647/ad70e7
Gurpreet Singh, Trishala Mitra, Søren P Madsen, Aurélien Dantan
We theoretically investigate the design of thin subwavelength gratings possessing high-reflectivity and high-Q resonances when illuminated at normal incidence by a Gaussian beam. We compare the performances of single-period and dual-period rectangular gratings using finite element method-based optimization and predict a close to two orders of magnitude improvement (×90) in their transmission loss-linewidth product, which is the relevant figure of merit for e.g. resonant mirror-based microcavity applications.
{"title":"Highly reflective and high-Q thin resonant subwavelength gratings","authors":"Gurpreet Singh, Trishala Mitra, Søren P Madsen, Aurélien Dantan","doi":"10.1088/2515-7647/ad70e7","DOIUrl":"https://doi.org/10.1088/2515-7647/ad70e7","url":null,"abstract":"We theoretically investigate the design of thin subwavelength gratings possessing high-reflectivity and high-<italic toggle=\"yes\">Q</italic> resonances when illuminated at normal incidence by a Gaussian beam. We compare the performances of single-period and dual-period rectangular gratings using finite element method-based optimization and predict a close to two orders of magnitude improvement (×90) in their transmission loss-linewidth product, which is the relevant figure of merit for e.g. resonant mirror-based microcavity applications.","PeriodicalId":44008,"journal":{"name":"Journal of Physics-Photonics","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-23DOI: 10.1088/2515-7647/ad6ed3
Benjamin R Anderson, Andrew O’Kins, Kostiantyn Makrasnov, Rebecca Udby, Patrick Price, Hergen Eilers
We have developed a modular graphical user interface (GUI)-based program for use in genetic algorithm-based feedback-assisted wavefront shaping. The program uses a class-based structure to separate out the universal modules (e.g. GUI, multithreading, optimization algorithms) and hardware-specific modules (e.g. code for different SLMs and cameras). This modular design makes the program easily adaptable to a wide range of lab equipment, while providing easy access to a GUI, multithreading, and three optimization algorithms (phase-stepping, simple genetic, and microgenetic).
{"title":"A modular GUI-based program for genetic algorithm-based feedback-assisted wavefront shaping","authors":"Benjamin R Anderson, Andrew O’Kins, Kostiantyn Makrasnov, Rebecca Udby, Patrick Price, Hergen Eilers","doi":"10.1088/2515-7647/ad6ed3","DOIUrl":"https://doi.org/10.1088/2515-7647/ad6ed3","url":null,"abstract":"We have developed a modular graphical user interface (GUI)-based program for use in genetic algorithm-based feedback-assisted wavefront shaping. The program uses a class-based structure to separate out the universal modules (e.g. GUI, multithreading, optimization algorithms) and hardware-specific modules (e.g. code for different SLMs and cameras). This modular design makes the program easily adaptable to a wide range of lab equipment, while providing easy access to a GUI, multithreading, and three optimization algorithms (phase-stepping, simple genetic, and microgenetic).","PeriodicalId":44008,"journal":{"name":"Journal of Physics-Photonics","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-23DOI: 10.1088/2515-7647/ad6dc0
Sébastien M Popoff, Rodrigo Gutiérrez-Cuevas, Yaron Bromberg, Maxime W Matthés
Digital micromirror devices have gained popularity in wavefront shaping, offering a high frame rate alternative to liquid crystal spatial light modulators. They are relatively inexpensive, offer high resolution, are easy to operate, and a single device can be used in a broad optical bandwidth. However, some technical drawbacks must be considered to achieve optimal performance. These issues, often undocumented by manufacturers, mostly stem from the device’s original design for video projection applications. Herein, we present a guide to characterize and mitigate these effects. Our focus is on providing simple and practical solutions that can be easily incorporated into a typical wavefront shaping setup.
{"title":"A practical guide to digital micro-mirror devices (DMDs) for wavefront shaping","authors":"Sébastien M Popoff, Rodrigo Gutiérrez-Cuevas, Yaron Bromberg, Maxime W Matthés","doi":"10.1088/2515-7647/ad6dc0","DOIUrl":"https://doi.org/10.1088/2515-7647/ad6dc0","url":null,"abstract":"Digital micromirror devices have gained popularity in wavefront shaping, offering a high frame rate alternative to liquid crystal spatial light modulators. They are relatively inexpensive, offer high resolution, are easy to operate, and a single device can be used in a broad optical bandwidth. However, some technical drawbacks must be considered to achieve optimal performance. These issues, often undocumented by manufacturers, mostly stem from the device’s original design for video projection applications. Herein, we present a guide to characterize and mitigate these effects. Our focus is on providing simple and practical solutions that can be easily incorporated into a typical wavefront shaping setup.","PeriodicalId":44008,"journal":{"name":"Journal of Physics-Photonics","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-22DOI: 10.1088/2515-7647/ad6ed2
Michael Raju, Baptiste Jayet, Stefan Andersson-Engels
We developed a 2D Finite-difference time-domain (FDTD) method for modeling a space-time modulated guidestar targeting wavefront shaping applications in disordered media. Space-time modulation in general (a particular example being the acousto-optic effect) is used here as a guidestar for the transverse confinement of light around the tagged region surrounded by disorder. Together with the guidestar, the iterative optical phase conjugation (IOPC) method is used to overcome the diffusion of light due to multiple scattering. A phase sensitive lock-in detection technique is utilized to estimate the steady-state amplitude and phase of the modulated wavefronts emerging from the guidestar region continuously operating in the Raman-Nath regime. As the IOPC scheme naturally converges to the maximally transmitting eigenchannel profile, one could use the position of the guidestar within the disorder to channelize the maximal transmission through the tagged region. The associated code developed in MATLAB® is provided as an open source (The MIT License) package. The code package is referred by the acronym STAR-FDTD where STAR stands for Space-Time modulated Acousto-optic guidestaR.
我们开发了一种二维有限差分时域（FDTD）方法，用于模拟无序介质中波前整形应用的时空调制导星。时空调制一般（声光效应就是一个特别的例子）在这里被用作光在无序环绕的标记区域周围横向限制的导星。迭代光学相位共轭（IOPC）方法与导星一起用于克服多重散射导致的光扩散。利用相位敏感的锁相检测技术来估算从导星区域出现的调制波面的稳态振幅和相位，这些波面在拉曼-纳特机制下持续工作。由于 IOPC 方案会自然收敛到最大传输特征通道轮廓，因此可以利用导星在无序状态中的位置来引导通过标记区域的最大传输。用 MATLAB® 开发的相关代码以开放源代码（MIT 许可）的形式提供。代码包的缩写为 STAR-FDTD，其中 STAR 代表时空调制声光导引星。
{"title":"STAR-FDTD: space-time modulated acousto-optic guidestar in disordered media","authors":"Michael Raju, Baptiste Jayet, Stefan Andersson-Engels","doi":"10.1088/2515-7647/ad6ed2","DOIUrl":"https://doi.org/10.1088/2515-7647/ad6ed2","url":null,"abstract":"We developed a 2D Finite-difference time-domain (FDTD) method for modeling a space-time modulated guidestar targeting wavefront shaping applications in disordered media. Space-time modulation in general (a particular example being the acousto-optic effect) is used here as a guidestar for the transverse confinement of light around the tagged region surrounded by disorder. Together with the guidestar, the iterative optical phase conjugation (IOPC) method is used to overcome the diffusion of light due to multiple scattering. A phase sensitive lock-in detection technique is utilized to estimate the steady-state amplitude and phase of the modulated wavefronts emerging from the guidestar region continuously operating in the Raman-Nath regime. As the IOPC scheme naturally converges to the maximally transmitting eigenchannel profile, one could use the position of the guidestar within the disorder to channelize the maximal transmission through the tagged region. The associated code developed in MATLAB<sup>®</sup> is provided as an open source (The MIT License) package. The code package is referred by the acronym STAR-FDTD where STAR stands for <bold>S</bold>pace-<bold>T</bold>ime modulated <bold>A</bold>cousto-optic guidesta<bold>R</bold>.","PeriodicalId":44008,"journal":{"name":"Journal of Physics-Photonics","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-14DOI: 10.1088/2515-7647/ad6abc
Claudia Daffara, Dario Ambrosini
Nondestructive optical techniques are crucial in heritage science for monitoring the condition of artworks in full field. Various imaging methods based on infrared and interferometry techniques have been proposed, but they often require specialized training and expensive equipment. This paper explores the emerging field of smartphone science and its potential to revolutionize artwork diagnostics, especially for cultural institutions with limited budgets. The smartphone science approach is divided into using the device ‘as is’ or enhancing it with add-on sensors. After a concise overview of smartphone sensing in different fields, the paper demonstrates smartphone-based optical diagnostics on traditional wooden painting models, employing coherent techniques like laser speckle imaging and moiré fringe technique, and infrared techniques like reflectography and thermography. The comparison of obtained results with established instrumentation in the field clearly shows that smartphone-based diagnostics have the potential to greatly contribute to cultural heritage preservation and conservation, transforming the field’s accessibility and cost-effectiveness.
{"title":"Smartphone-based diagnostics with coherent and infrared imaging for cultural heritage","authors":"Claudia Daffara, Dario Ambrosini","doi":"10.1088/2515-7647/ad6abc","DOIUrl":"https://doi.org/10.1088/2515-7647/ad6abc","url":null,"abstract":"Nondestructive optical techniques are crucial in heritage science for monitoring the condition of artworks in full field. Various imaging methods based on infrared and interferometry techniques have been proposed, but they often require specialized training and expensive equipment. This paper explores the emerging field of smartphone science and its potential to revolutionize artwork diagnostics, especially for cultural institutions with limited budgets. The smartphone science approach is divided into using the device ‘as is’ or enhancing it with add-on sensors. After a concise overview of smartphone sensing in different fields, the paper demonstrates smartphone-based optical diagnostics on traditional wooden painting models, employing coherent techniques like laser speckle imaging and moiré fringe technique, and infrared techniques like reflectography and thermography. The comparison of obtained results with established instrumentation in the field clearly shows that smartphone-based diagnostics have the potential to greatly contribute to cultural heritage preservation and conservation, transforming the field’s accessibility and cost-effectiveness.","PeriodicalId":44008,"journal":{"name":"Journal of Physics-Photonics","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-13DOI: 10.1088/2515-7647/ad68de
Yudong Ren, Xinrui Li, Ning Han, Li Zhang, Rui Zhao, Qiaolu Chen, Yuze Hu, Mingyu Tong, Song Han, Yihao Yang
Topological photonics offers a powerful platform for next-generation nanophotonic chips, capitalizing on their remarkable resilience to disorder and defects. Among the two-dimensional (2D) photonic topological insulators, valley-Hall (VH) and pseudo-spin-Hall (PSH) topological insulators have emerged as the most practical designs, as they do not require breaking time-reversal symmetry. These photonic topological insulators support robust edge states, demonstrating promising potential for a wide range of applications, from on-chip communication to optical computing and sensing. However, the conversion between distinct topological phases (VH and PSH) in terahertz (THz) band has not been achieved. Here we experimentally demonstrate a THz on-chip spin–valley converter through adiabatic evolution in 2D parameter space without closing the bulk bandgap. By leveraging the adiabatic phase transition, we confirm the high-efficiency conversion between two valley states in a valley–spin–valley converter. In addition, we verify the robustness of THz PSH topological energy transport through sharply twisted corners. Our findings not only advance the understanding of topological phases in photonics but also hold promise for the development of innovative photonic devices with enhanced performance and functionality.
{"title":"Topological THz on-chip valley–spin converter","authors":"Yudong Ren, Xinrui Li, Ning Han, Li Zhang, Rui Zhao, Qiaolu Chen, Yuze Hu, Mingyu Tong, Song Han, Yihao Yang","doi":"10.1088/2515-7647/ad68de","DOIUrl":"https://doi.org/10.1088/2515-7647/ad68de","url":null,"abstract":"Topological photonics offers a powerful platform for next-generation nanophotonic chips, capitalizing on their remarkable resilience to disorder and defects. Among the two-dimensional (2D) photonic topological insulators, valley-Hall (VH) and pseudo-spin-Hall (PSH) topological insulators have emerged as the most practical designs, as they do not require breaking time-reversal symmetry. These photonic topological insulators support robust edge states, demonstrating promising potential for a wide range of applications, from on-chip communication to optical computing and sensing. However, the conversion between distinct topological phases (VH and PSH) in terahertz (THz) band has not been achieved. Here we experimentally demonstrate a THz on-chip spin–valley converter through adiabatic evolution in 2D parameter space without closing the bulk bandgap. By leveraging the adiabatic phase transition, we confirm the high-efficiency conversion between two valley states in a valley–spin–valley converter. In addition, we verify the robustness of THz PSH topological energy transport through sharply twisted corners. Our findings not only advance the understanding of topological phases in photonics but also hold promise for the development of innovative photonic devices with enhanced performance and functionality.","PeriodicalId":44008,"journal":{"name":"Journal of Physics-Photonics","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-07DOI: 10.1088/2515-7647/ad6963
Vaswati Biswas and R Vijaya
A plasmonic metasurface containing nanobumps of sub-wavelength feature size arranged in a hexagonal pattern on a flexible substrate and covered with a thin film of gold is investigated as a refractive index (RI) sensor. The chosen polymer patterns coated with gold aid in activating the surface plasmon polariton modes. Using numerical calculations, it is shown that this surface can exhibit plasmonic effect with extremely shallow pattern height of 92.5 nm and minimal thickness of 25 nm of gold over it. The excitation of the plasmonic modes is confirmed using electric field profiles calculated at the relevant wavelengths. As the surface is highly sensitive to changes in the cladding index, and the chosen design aids in exciting three plasmon modes that are suitably well-separated in wavelength, this surface can be used for an extremely wide range of RI sensing because each mode contributes uniquely to a different range of RI. The results establish that the metasurface is suitable for a variety of applications, including gas detection with a sensitivity of 633 nm RIU−1 using mode-1, identifying SARS-CoV-2 viral molecules with a sensitivity of 428 nm RIU−1 using mode-2 and 238 nm RIU−1 using mode-3, and discriminating between normal and diseased brain tissues in the cerebrospinal fluid in the high-index range using mode-3. The prototype metasurface is made using a cost-effective soft lithography technique using an economical master mould. The inexpensive technique of fabrication, use of very thin metal film, and wavelength of detection lying within the visible to near infrared range imply a low-cost sensor. The structural and optical characterization of the prototype validates the numerical study of the sample.
{"title":"Multi-modal flexible and inexpensive plasmonic metasurface for wide range of refractive index sensing","authors":"Vaswati Biswas and R Vijaya","doi":"10.1088/2515-7647/ad6963","DOIUrl":"https://doi.org/10.1088/2515-7647/ad6963","url":null,"abstract":"A plasmonic metasurface containing nanobumps of sub-wavelength feature size arranged in a hexagonal pattern on a flexible substrate and covered with a thin film of gold is investigated as a refractive index (RI) sensor. The chosen polymer patterns coated with gold aid in activating the surface plasmon polariton modes. Using numerical calculations, it is shown that this surface can exhibit plasmonic effect with extremely shallow pattern height of 92.5 nm and minimal thickness of 25 nm of gold over it. The excitation of the plasmonic modes is confirmed using electric field profiles calculated at the relevant wavelengths. As the surface is highly sensitive to changes in the cladding index, and the chosen design aids in exciting three plasmon modes that are suitably well-separated in wavelength, this surface can be used for an extremely wide range of RI sensing because each mode contributes uniquely to a different range of RI. The results establish that the metasurface is suitable for a variety of applications, including gas detection with a sensitivity of 633 nm RIU−1 using mode-1, identifying SARS-CoV-2 viral molecules with a sensitivity of 428 nm RIU−1 using mode-2 and 238 nm RIU−1 using mode-3, and discriminating between normal and diseased brain tissues in the cerebrospinal fluid in the high-index range using mode-3. The prototype metasurface is made using a cost-effective soft lithography technique using an economical master mould. The inexpensive technique of fabrication, use of very thin metal film, and wavelength of detection lying within the visible to near infrared range imply a low-cost sensor. The structural and optical characterization of the prototype validates the numerical study of the sample.","PeriodicalId":44008,"journal":{"name":"Journal of Physics-Photonics","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-06DOI: 10.1088/2515-7647/ad68dd
Daniele Ancora, Alessandro Zunino, Giuseppe Vicidomini and Alvaro H Crevenna
Confocal laser scanning microscopy (CLSM) stands out as one of the most widely used microscopy techniques thanks to its three-dimensional imaging capability and its sub-diffraction spatial resolution, achieved through the closure of a pinhole in front of a single-element detector. However, the pinhole also rejects useful photons, and beating the diffraction limit comes at the price of irremediably compromising the signal-to-noise ratio (SNR) of the data. Image scanning microscopy (ISM) emerged as the rational evolution of CLSM, exploiting a small array detector in place of the pinhole and the single-element detector. Each sensitive element is small enough to achieve sub-diffraction resolution through the confocal effect, but the size of the whole detector is large enough to guarantee excellent collection efficiency and SNR. However, the raw data produced by an ISM setup consists of a 4D dataset, which can be seen as a set of confocal-like images. Thus, fusing the dataset into a single super-resolved image requires a dedicated reconstruction algorithm. Conventional methods are multi-image deconvolution, which requires prior knowledge of the system point spread functions (PSFs), or adaptive pixel reassignment (APR), which is effective only on a limited range of experimental conditions. In this work, we describe and validate a novel concept for ISM image reconstruction based on autocorrelation inversion. We leverage unique properties of the autocorrelation to discard low-frequency components and maximize the resolution of the reconstructed image without any assumption on the image or any knowledge of the PSF. Our results push the quality of the ISM reconstruction beyond the level provided by APR and open new perspectives for multi-dimensional image processing.
共焦激光扫描显微镜（CLSM）是应用最广泛的显微镜技术之一，这要归功于它的三维成像能力和亚衍射空间分辨率。然而，针孔也会阻挡有用的光子，突破衍射极限的代价是数据的信噪比（SNR）受到不可挽回的损害。图像扫描显微镜（ISM）的出现是 CLSM 的合理发展，它利用小型阵列探测器取代了针孔和单元素探测器。每个敏感元件都足够小，可以通过共焦效应达到亚衍射分辨率，但整个探测器的尺寸足够大，可以保证出色的收集效率和信噪比。然而，ISM 设置产生的原始数据由 4D 数据集组成，可以看作是一组类似共焦的图像。因此，将数据集融合为单个超分辨图像需要专门的重建算法。传统的方法有多图像解卷积（需要事先了解系统点扩散函数（PSF））或自适应像素重配（APR），后者仅在有限的实验条件下有效。在这项工作中，我们描述并验证了一种基于自相关反演的 ISM 图像重建新概念。我们利用自相关的独特性质摒弃了低频成分，最大限度地提高了重建图像的分辨率，而无需对图像或 PSF 做任何假设。我们的研究结果使 ISM 重建的质量超越了 APR 所提供的水平，为多维图像处理开辟了新的前景。
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