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Review Articles|27 Article(s)
Revolutionizing optical imaging: computational imaging via deep learning
Xiyuan Luo, Sen Wang, Jinpeng Liu, Xue Dong, Piao He, Qingyu Yang, Xi Chen, Feiyan Zhou, Tong Zhang, Shijie Feng, Pingli Han, Zhiming Zhou, Meng Xiang, Jiaming Qian, Haigang Ma, Shun Zhou, Linpeng Lu, Chao Zuo, Zihan Geng, Yi Wei, and Fei Liu
The current state of traditional optoelectronic imaging technology is constrained by the inherent limitations of its hardware. These limitations pose significant challenges in acquiring higher-dimensional information and reconstructing accurate images, particularly in applications such as scattering imaging, super-resolution, and complex scene reconstruction. However, the rapid development and widespread adoption of deep learning are reshaping the field of optical imaging through computational imaging technology. Data-driven computational imaging has ushered in a paradigm shift by leveraging the nonlinear expression and feature learning capabilities of neural networks. This approach transcends the limitations of conventional physical models, enabling the adaptive extraction of critical features directly from data. As a result, computational imaging overcomes the traditional “what you see is what you get” paradigm, paving the way for more compact optical system designs, broader information acquisition, and improved image reconstruction accuracy. These advancements have significantly enhanced the interpretation of high-dimensional light-field information and the processing of complex images. This review presents a comprehensive analysis of the integration of deep learning and computational imaging, emphasizing its transformative potential in three core areas: computational optical system design, high-dimensional information interpretation, and image enhancement and processing. Additionally, this review addresses the challenges and future directions of this cutting-edge technology, providing novel insights into interdisciplinary imaging research. The current state of traditional optoelectronic imaging technology is constrained by the inherent limitations of its hardware. These limitations pose significant challenges in acquiring higher-dimensional information and reconstructing accurate images, particularly in applications such as scattering imaging, super-resolution, and complex scene reconstruction. However, the rapid development and widespread adoption of deep learning are reshaping the field of optical imaging through computational imaging technology. Data-driven computational imaging has ushered in a paradigm shift by leveraging the nonlinear expression and feature learning capabilities of neural networks. This approach transcends the limitations of conventional physical models, enabling the adaptive extraction of critical features directly from data. As a result, computational imaging overcomes the traditional “what you see is what you get” paradigm, paving the way for more compact optical system designs, broader information acquisition, and improved image reconstruction accuracy. These advancements have significantly enhanced the interpretation of high-dimensional light-field information and the processing of complex images. This review presents a comprehensive analysis of the integration of deep learning and computational imaging, emphasizing its transformative potential in three core areas: computational optical system design, high-dimensional information interpretation, and image enhancement and processing. Additionally, this review addresses the challenges and future directions of this cutting-edge technology, providing novel insights into interdisciplinary imaging research.
Photonics Insights
- Publication Date: Apr. 08, 2025
- Vol. 4, Issue 2, R03 (2025)
Exceptional-point optics with loss engineering|Story Video
Shaohua Dong, Heng Wei, Zhipeng Li, Guangtao Cao, Kun Xue, Yang Chen, and Cheng-Wei Qiu
Loss is usually considered a problem for photonics, which can seriously deteriorate the performance of most optical devices, and thus has to be suppressed. However, in non-Hermitian passive optical systems without gain, when both eigenvalues and eigenvectors coalesce to form exceptional points (EPs), the addition of loss may, counterintuitively, bring unique advantages, such as improved noise resistance and more stable operation. In this review, we first briefly introduce the underlying mechanisms leading to passive EPs and then examine several implementations based on different electromagnetic structures, including cavities, waveguides, and metasurfaces. We highlight the introduction of losses in each case and discuss their benefits. Finally, we also provide our thoughts on the current limits for those passive realizations as well as potential future projects. Loss is usually considered a problem for photonics, which can seriously deteriorate the performance of most optical devices, and thus has to be suppressed. However, in non-Hermitian passive optical systems without gain, when both eigenvalues and eigenvectors coalesce to form exceptional points (EPs), the addition of loss may, counterintuitively, bring unique advantages, such as improved noise resistance and more stable operation. In this review, we first briefly introduce the underlying mechanisms leading to passive EPs and then examine several implementations based on different electromagnetic structures, including cavities, waveguides, and metasurfaces. We highlight the introduction of losses in each case and discuss their benefits. Finally, we also provide our thoughts on the current limits for those passive realizations as well as potential future projects.
Photonics Insights
- Publication Date: Mar. 25, 2025
- Vol. 4, Issue 1, R02 (2025)
High-spatiotemporal-resolution structured illumination microscopy: principles, instrumentation, and applications|On the Cover , Story Video
Han Wang, Wenshu Wang, Xinzhu Xu, Meiqi Li, and Peng Xi
Among super-resolution microscopy techniques, structured illumination microscopy (SIM) shows great advances in low phototoxicity, high speed, and excellent performance in long-term dynamic observation, making it especially suitable for live-cell imaging. This review delves into the principles, instrumentation, and applications of SIM, highlighting its capabilities in achieving high spatiotemporal resolution. Two types of structured illumination mechanics are employed: (1) stripe-based SIM, where the illumination stripes are formed through interference or projection, with extended resolution achieved through Fourier-domain extension; (2) point-scanning-based SIM, where illumination patterns are generated through the projection of the focal point or focal array, with extended resolution achieved through photon reassignment. We discuss the evolution of SIM from mechanical to high-speed photoelectric devices, such as spatial light modulators, digital micromirror devices, galvanometers, etc., which significantly enhance imaging speed, resolution, and modulation flexibility. The review also explores SIM’s applications in biological research, particularly in live-cell imaging and cellular interaction studies, providing insights into disease mechanisms and cellular functions. We conclude by outlining the future directions of SIM in life sciences. With the advancement of imaging techniques and reconstruction algorithms, SIM is poised to bring revolutionary impacts to frontier research fields, offering new avenues for exploring the intricacies of cellular biology. Among super-resolution microscopy techniques, structured illumination microscopy (SIM) shows great advances in low phototoxicity, high speed, and excellent performance in long-term dynamic observation, making it especially suitable for live-cell imaging. This review delves into the principles, instrumentation, and applications of SIM, highlighting its capabilities in achieving high spatiotemporal resolution. Two types of structured illumination mechanics are employed: (1) stripe-based SIM, where the illumination stripes are formed through interference or projection, with extended resolution achieved through Fourier-domain extension; (2) point-scanning-based SIM, where illumination patterns are generated through the projection of the focal point or focal array, with extended resolution achieved through photon reassignment. We discuss the evolution of SIM from mechanical to high-speed photoelectric devices, such as spatial light modulators, digital micromirror devices, galvanometers, etc., which significantly enhance imaging speed, resolution, and modulation flexibility. The review also explores SIM’s applications in biological research, particularly in live-cell imaging and cellular interaction studies, providing insights into disease mechanisms and cellular functions. We conclude by outlining the future directions of SIM in life sciences. With the advancement of imaging techniques and reconstruction algorithms, SIM is poised to bring revolutionary impacts to frontier research fields, offering new avenues for exploring the intricacies of cellular biology.
Photonics Insights
- Publication Date: Mar. 24, 2025
- Vol. 4, Issue 1, R01 (2025)
Microcomb technology: from principles to applications|Story Video
Haowen Shu, Bitao Shen, Huajin Chang, Junhao Han, Jiong Xiao, and Xingjun Wang
Integrated microcombs bring a parallel and coherent optical frequency comb to compact chip-scale devices. They offer promising prospects for mass-produced comb sources in a compact, power-efficient, and robust manner, benefiting many basic research and practical applications. In the past two decades, they have been utilized in many traditional fields, such as high-capacity parallel communication, optical frequency synthesis, frequency metrology, precision spectroscopy, and emerging fields like distance ranging, optical computing, microwave photonics, and molecule detection. In this review, we briefly introduce microcombs, including their physical model, formation dynamics, generation methods, materials and fabrications, design principles, and advanced applications. We also systematically summarize the field of integrated optical combs and evaluate the remaining challenges and prospects in each aspect. Integrated microcombs bring a parallel and coherent optical frequency comb to compact chip-scale devices. They offer promising prospects for mass-produced comb sources in a compact, power-efficient, and robust manner, benefiting many basic research and practical applications. In the past two decades, they have been utilized in many traditional fields, such as high-capacity parallel communication, optical frequency synthesis, frequency metrology, precision spectroscopy, and emerging fields like distance ranging, optical computing, microwave photonics, and molecule detection. In this review, we briefly introduce microcombs, including their physical model, formation dynamics, generation methods, materials and fabrications, design principles, and advanced applications. We also systematically summarize the field of integrated optical combs and evaluate the remaining challenges and prospects in each aspect.
Photonics Insights
- Publication Date: Dec. 31, 2024
- Vol. 3, Issue 4, R09 (2024)
Spatiotemporal optical wavepackets: from concepts to applications|On the Cover , Story Video
Xin Liu, Qian Cao, and Qiwen Zhan
Spatiotemporal optical wavepackets refer to light fields with sophisticated structures in both space and time. The ability to produce such spatiotemporally structured optical wavepackets on demand attracted rapidly increasing interest as it may unravel a variety of fundamental physical effects and applications. Traditionally, pulsed laser fields are treated as spatiotemporally separable waveform solutions to Maxwell’s equations. Recently, more generalized spatiotemporally non-separable solutions have gained attention due to their remarkable properties. This review aims to provide essential insights into sculpting light in the space–time domain to create customized spatiotemporal structures and highlights the recent advances in the generation, manipulation, and characterization of increasingly complex spatiotemporal wavepackets. These spatiotemporally non-separable light fields with diverse geometric and topological structures exhibit unique physical properties during propagation, focusing, and light–matter interactions. Various novel results and their broad potential applications as well as an outlook for future trends and challenges in this field are presented. Spatiotemporal optical wavepackets refer to light fields with sophisticated structures in both space and time. The ability to produce such spatiotemporally structured optical wavepackets on demand attracted rapidly increasing interest as it may unravel a variety of fundamental physical effects and applications. Traditionally, pulsed laser fields are treated as spatiotemporally separable waveform solutions to Maxwell’s equations. Recently, more generalized spatiotemporally non-separable solutions have gained attention due to their remarkable properties. This review aims to provide essential insights into sculpting light in the space–time domain to create customized spatiotemporal structures and highlights the recent advances in the generation, manipulation, and characterization of increasingly complex spatiotemporal wavepackets. These spatiotemporally non-separable light fields with diverse geometric and topological structures exhibit unique physical properties during propagation, focusing, and light–matter interactions. Various novel results and their broad potential applications as well as an outlook for future trends and challenges in this field are presented.
Photonics Insights
- Publication Date: Dec. 28, 2024
- Vol. 3, Issue 4, R08 (2024)
Electrically tunable optical metasurfaces|Story Video
Fei Ding, Chao Meng, and Sergey I. Bozhevolnyi
Optical metasurfaces have emerged as a groundbreaking technology in photonics, offering unparalleled control over light–matter interactions at the subwavelength scale with ultrathin surface nanostructures and thereby giving birth to flat optics. While most reported optical metasurfaces are static, featuring well-defined optical responses determined by their compositions and configurations set during fabrication, dynamic optical metasurfaces with reconfigurable functionalities by applying thermal, electrical, or optical stimuli have become increasingly more in demand and moved to the forefront of research and development. Among various types of dynamically controlled metasurfaces, electrically tunable optical metasurfaces have shown great promise due to their fast response time, low power consumption, and compatibility with existing electronic control systems, offering unique possibilities for dynamic tunability of light–matter interactions via electrical modulation. Here we provide a comprehensive overview of the state-of-the-art design methodologies and technologies explored in this rapidly evolving field. Our work delves into the fundamental principles of electrical modulation, various materials and mechanisms enabling tunability, and representative applications for active light-field manipulation, including optical amplitude and phase modulators, tunable polarization optics and wavelength filters, and dynamic wave-shaping optics, including holograms and displays. The review terminates with our perspectives on the future development of electrically triggered optical metasurfaces. Optical metasurfaces have emerged as a groundbreaking technology in photonics, offering unparalleled control over light–matter interactions at the subwavelength scale with ultrathin surface nanostructures and thereby giving birth to flat optics. While most reported optical metasurfaces are static, featuring well-defined optical responses determined by their compositions and configurations set during fabrication, dynamic optical metasurfaces with reconfigurable functionalities by applying thermal, electrical, or optical stimuli have become increasingly more in demand and moved to the forefront of research and development. Among various types of dynamically controlled metasurfaces, electrically tunable optical metasurfaces have shown great promise due to their fast response time, low power consumption, and compatibility with existing electronic control systems, offering unique possibilities for dynamic tunability of light–matter interactions via electrical modulation. Here we provide a comprehensive overview of the state-of-the-art design methodologies and technologies explored in this rapidly evolving field. Our work delves into the fundamental principles of electrical modulation, various materials and mechanisms enabling tunability, and representative applications for active light-field manipulation, including optical amplitude and phase modulators, tunable polarization optics and wavelength filters, and dynamic wave-shaping optics, including holograms and displays. The review terminates with our perspectives on the future development of electrically triggered optical metasurfaces.
Photonics Insights
- Publication Date: Sep. 27, 2024
- Vol. 3, Issue 3, R07 (2024)
Image reconstruction from photoacoustic projections|Story Video
Chao Tian, Kang Shen, Wende Dong, Fei Gao, Kun Wang, Jiao Li, Songde Liu, Ting Feng, Chengbo Liu, Changhui Li, Meng Yang, Sheng Wang, and Jie Tian
Photoacoustic computed tomography (PACT) is a rapidly developing biomedical imaging modality and has attracted substantial attention in recent years. Image reconstruction from photoacoustic projections plays a critical role in image formation in PACT. Here we review six major classes of image reconstruction approaches developed in the past three decades, including delay and sum, filtered back projection, series expansion, time reversal, iterative reconstruction, and deep-learning-based reconstruction. The principal ideas and implementations of the algorithms are summarized, and their reconstruction performances under different imaging scenarios are compared. Major challenges, future directions, and perspectives for the development of image reconstruction algorithms in PACT are also discussed. This review provides a self-contained reference guide for beginners and specialists in the photoacoustic community, to facilitate the development and application of novel photoacoustic image reconstruction algorithms. Photoacoustic computed tomography (PACT) is a rapidly developing biomedical imaging modality and has attracted substantial attention in recent years. Image reconstruction from photoacoustic projections plays a critical role in image formation in PACT. Here we review six major classes of image reconstruction approaches developed in the past three decades, including delay and sum, filtered back projection, series expansion, time reversal, iterative reconstruction, and deep-learning-based reconstruction. The principal ideas and implementations of the algorithms are summarized, and their reconstruction performances under different imaging scenarios are compared. Major challenges, future directions, and perspectives for the development of image reconstruction algorithms in PACT are also discussed. This review provides a self-contained reference guide for beginners and specialists in the photoacoustic community, to facilitate the development and application of novel photoacoustic image reconstruction algorithms.
Photonics Insights
- Publication Date: Sep. 26, 2024
- Vol. 3, Issue 3, R06 (2024)
Integrated structured light manipulation|On the Cover
Jian Wang, Kang Li, and Zhiqiang Quan
Structured light, also known as tailored light, shaped light, sculpted light, or custom light, refers to a series of special light beams with spatially variant amplitudes and phases, polarization distributions, or more general spatiotemporal profiles. In the past decades, structured light featuring distinct properties and unique spatial or spatiotemporal structures has grown into a significant research field and given rise to many developments from fundamentals to applications. Very recently, integrated structured light manipulation has become an important trend in the frontier of light field manipulation and attracted increasing interest as a highly promising technique for shaping structured light in an integrated, compact, and miniaturized manner. In this article, we give a comprehensive overview of recent advances in integrated structured light manipulation (generation, processing, detection, and application). After briefly introducing the basic concept and development history of structured light, we present representative works in four important aspects of integrated structured light manipulation, including multiple types of integrated structured light generation, many sorts of integrated structured light processing, diverse forms of integrated structured light detection, and various kinds of integrated structured light applications. We focus on summarizing the progress of integrated structured light manipulation from basic theories to cutting-edge technologies, to key devices, and to a wide variety of applications, from orbital angular momentum carrying light beams to more general structured light beams, from passive to active integration platforms, from micro-nano structures and metasurfaces to 2D photonic integrated circuits and 3D photonic chips, from in-plane to out-of-plane, from multiplexing to transformation, from linear to nonlinear, from classical to quantum, from optical communications to optical holography, imaging, microscopy, trapping, tweezers, metrology, etc. Finally, we also discuss in detail the future trends, opportunities, challenges, and solutions, and give a vision for integrated structured light manipulation. Structured light, also known as tailored light, shaped light, sculpted light, or custom light, refers to a series of special light beams with spatially variant amplitudes and phases, polarization distributions, or more general spatiotemporal profiles. In the past decades, structured light featuring distinct properties and unique spatial or spatiotemporal structures has grown into a significant research field and given rise to many developments from fundamentals to applications. Very recently, integrated structured light manipulation has become an important trend in the frontier of light field manipulation and attracted increasing interest as a highly promising technique for shaping structured light in an integrated, compact, and miniaturized manner. In this article, we give a comprehensive overview of recent advances in integrated structured light manipulation (generation, processing, detection, and application). After briefly introducing the basic concept and development history of structured light, we present representative works in four important aspects of integrated structured light manipulation, including multiple types of integrated structured light generation, many sorts of integrated structured light processing, diverse forms of integrated structured light detection, and various kinds of integrated structured light applications. We focus on summarizing the progress of integrated structured light manipulation from basic theories to cutting-edge technologies, to key devices, and to a wide variety of applications, from orbital angular momentum carrying light beams to more general structured light beams, from passive to active integration platforms, from micro-nano structures and metasurfaces to 2D photonic integrated circuits and 3D photonic chips, from in-plane to out-of-plane, from multiplexing to transformation, from linear to nonlinear, from classical to quantum, from optical communications to optical holography, imaging, microscopy, trapping, tweezers, metrology, etc. Finally, we also discuss in detail the future trends, opportunities, challenges, and solutions, and give a vision for integrated structured light manipulation.
Photonics Insights
- Publication Date: Sep. 17, 2024
- Vol. 3, Issue 3, R05 (2024)
Advanced manufacturing of dielectric meta-devices
Wenhong Yang, Junxiao Zhou, Din Ping Tsai, and Shumin Xiao
Metasurfaces, composed of two-dimensional nanostructures, exhibit remarkable capabilities in shaping wavefronts, encompassing phase, amplitude, and polarization. This unique proficiency heralds a transformative paradigm shift in the domain of next-generation optics and photonics, culminating in the development of flat and ultrathin optical devices. Particularly noteworthy is the all-dielectric-based metasurface, leveraging materials such as titanium dioxide, silicon, gallium arsenide, and silicon nitride, which finds extensive application in the design and implementation of high-performance optical devices, owing to its notable advantages, including a high refractive index, low ohmic loss, and cost-effectiveness. Furthermore, the remarkable growth in nanofabrication technologies allows for the exploration of new methods in metasurface fabrication, especially through wafer-scale nanofabrication technologies, thereby facilitating the realization of commercial applications for metasurfaces. This review provides a comprehensive overview of the latest advancements in state-of-the-art fabrication technologies in dielectric metasurface areas. These technologies, including standard nanolithography [e.g., electron beam lithography (EBL) and focused ion beam (FIB) lithography], advanced nanolithography (e.g., grayscale and scanning probe lithography), and large-scale nanolithography [e.g., nanoimprint and deep ultraviolet (DUV) lithography], are utilized to fabricate high-resolution, high-aspect-ratio, flexible, multilayer, slanted, and wafer-scale all-dielectric metasurfaces with intricate nanostructures. Ultimately, we conclude with a perspective on current cutting-edge nanofabrication technologies. Metasurfaces, composed of two-dimensional nanostructures, exhibit remarkable capabilities in shaping wavefronts, encompassing phase, amplitude, and polarization. This unique proficiency heralds a transformative paradigm shift in the domain of next-generation optics and photonics, culminating in the development of flat and ultrathin optical devices. Particularly noteworthy is the all-dielectric-based metasurface, leveraging materials such as titanium dioxide, silicon, gallium arsenide, and silicon nitride, which finds extensive application in the design and implementation of high-performance optical devices, owing to its notable advantages, including a high refractive index, low ohmic loss, and cost-effectiveness. Furthermore, the remarkable growth in nanofabrication technologies allows for the exploration of new methods in metasurface fabrication, especially through wafer-scale nanofabrication technologies, thereby facilitating the realization of commercial applications for metasurfaces. This review provides a comprehensive overview of the latest advancements in state-of-the-art fabrication technologies in dielectric metasurface areas. These technologies, including standard nanolithography [e.g., electron beam lithography (EBL) and focused ion beam (FIB) lithography], advanced nanolithography (e.g., grayscale and scanning probe lithography), and large-scale nanolithography [e.g., nanoimprint and deep ultraviolet (DUV) lithography], are utilized to fabricate high-resolution, high-aspect-ratio, flexible, multilayer, slanted, and wafer-scale all-dielectric metasurfaces with intricate nanostructures. Ultimately, we conclude with a perspective on current cutting-edge nanofabrication technologies.
Photonics Insights
- Publication Date: Jun. 30, 2024
- Vol. 3, Issue 2, R04 (2024)
Recent progress on structural coloration|On the Cover , Story Video
Yingjie Li, Jingtian Hu, Yixuan Zeng, Qinghai Song, Cheng-Wei Qiu, and Shumin Xiao
Structural coloration generates colors by the interaction between incident light and micro- or nano-scale structures. It has received tremendous interest for decades, due to advantages including robustness against bleaching and environmentally friendly properties (compared with conventional pigments and dyes). As a versatile coloration strategy, the tuning of structural colors based on micro- and nanoscale photonic structures has been extensively explored and can enable a broad range of applications including displays, anti-counterfeiting, and coating. However, scholarly research on structural colors has had limited impact on commercial products because of their disadvantages in cost, scalability, and fabrication. In this review, we analyze the key challenges and opportunities in the development of structural colors. We first summarize the fundamental mechanisms and design strategies for structural colors while reviewing the recent progress in realizing dynamic structural coloration. The promising potential applications including optical information processing and displays are also discussed while elucidating the most prominent challenges that prevent them from translating into technologies on the market. Finally, we address the new opportunities that are underexplored by the structural coloration community but can be achieved through multidisciplinary research within the emerging research areas. Structural coloration generates colors by the interaction between incident light and micro- or nano-scale structures. It has received tremendous interest for decades, due to advantages including robustness against bleaching and environmentally friendly properties (compared with conventional pigments and dyes). As a versatile coloration strategy, the tuning of structural colors based on micro- and nanoscale photonic structures has been extensively explored and can enable a broad range of applications including displays, anti-counterfeiting, and coating. However, scholarly research on structural colors has had limited impact on commercial products because of their disadvantages in cost, scalability, and fabrication. In this review, we analyze the key challenges and opportunities in the development of structural colors. We first summarize the fundamental mechanisms and design strategies for structural colors while reviewing the recent progress in realizing dynamic structural coloration. The promising potential applications including optical information processing and displays are also discussed while elucidating the most prominent challenges that prevent them from translating into technologies on the market. Finally, we address the new opportunities that are underexplored by the structural coloration community but can be achieved through multidisciplinary research within the emerging research areas.
Photonics Insights
- Publication Date: Apr. 22, 2024
- Vol. 3, Issue 2, R03 (2024)
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