Feedback-based wavefront shaping focuses light through scattering media by employing phase optimization algorithms.Genetic algorithms(GAs),inspired by the process of natural selection,are well suited for phase optimiz...Feedback-based wavefront shaping focuses light through scattering media by employing phase optimization algorithms.Genetic algorithms(GAs),inspired by the process of natural selection,are well suited for phase optimization in wavelfront shaping problems.In 2012,Conkey et al.first introduced a GA into feedback-based wavefront shaping to find the optimum phase map.Since then,due to its siuperior performance in noisy environment,the GA has been widely adopted by lots of implementations.However,there have been limited studies discussing and optimizing the detailed procedures of the GA.To fill this blank,in this study,we performed a thorough study on the performance of the GA for focusing light through scattering media.Using numerical tools,we evaluated certain procedures that can be potentially improved and provided guidance on how to choose certain parameters appropriately.This study is beneficial in improving the performance of wavefront shaping systems with GAs.展开更多
Wavefront shaping(WFS)techniques have been used as a powerful tool to control light propagation in complex media,including multimode fibers.In this paper,we propose a new application of WFS for multimode fber-based se...Wavefront shaping(WFS)techniques have been used as a powerful tool to control light propagation in complex media,including multimode fibers.In this paper,we propose a new application of WFS for multimode fber-based sensors.The use of a single multimode fiber alone,without any special fabrication,as a sensor based on the light intensity variations is not an easy task.The twist effect on multimode fiber is used as an example herein.Experimental results show that light intensity through the multimode fiber shows no direct relationship with the twist angle,but the correlation coefficient(CC)of speckle patterns does.Moreover,if WFS is applied to transform the spatially seemingly random light pattern at the exit of the multimode fiber into an optical focus.The focal pattern correlation and intensity both can serve to gauge the twist angle,with doubled measurement range and allowance of using a fast point detector to provide the feedback.With further development,WFS may find potentials to facilitate the development of multimode fber-based sensors in a variety of scenarios.展开更多
By manipulating the phase map of a wavefront of light using a spatial light modulator,the scattered light can be sharply focused on a specific target.Several iterative optimization algo-rithrns for obtaining the optim...By manipulating the phase map of a wavefront of light using a spatial light modulator,the scattered light can be sharply focused on a specific target.Several iterative optimization algo-rithrns for obtaining the optimumn phase map have been explored.However,there has not been a comparative study on the performance of these algorithms.In this paper,six optimization algorithms for wavefront shaping inchuding continuous sequential,partitioning algorithm,transmission matrix estimation method,particle swarm optimization,genetic algorithm(GA),and simulated annealing(SA)are discussed and compared based on their efficiency when introduced with various measurement noise levels.展开更多
Despite the unique advantages of optical microscopy for molecular specific high resolution imaging of living structure in both space and time,curent applications are mostly limited to research settings.This is due to ...Despite the unique advantages of optical microscopy for molecular specific high resolution imaging of living structure in both space and time,curent applications are mostly limited to research settings.This is due to the aberrations and multiple scattering that is induced by the inhomogeneous refractive boundaries that are inherent to biological systems.However,recent developments in adaptive optics and wavefront shaping have shown that high resolution optical imaging is not fundamentally limited only to the observation of single cells,but can be significantly enhanced to realize deep tissue imaging.To provide insight into how these two closely related fields can expand the limits of bio imaging,we review the recent progresses in their performance and applicable range of studies as well as potential future research directions to push the limits of deep tissuse imnaging.展开更多
We use feedback wavefront shaping technology to realize the multi-point uniform light focusing in three-dimensional(3D) space through scattering media only by loading the optimal mask once.General 3D spatial focusing ...We use feedback wavefront shaping technology to realize the multi-point uniform light focusing in three-dimensional(3D) space through scattering media only by loading the optimal mask once.General 3D spatial focusing needs to load the optimal mask multiple times to realize the spatial movement of the focal point and the uniformity of multi-point focusing cannot be guaranteed.First,we investigate the effects of speckle axial correlation and different axial distances on 3D spatial multi-point uniform focusing and propose possible solutions.Then we use our developed non-dominated sorting genetic algorithm suitable for 3D spatial focusing(S-NSGA) to verify the experiment of multi-point focusing in 3D space.This research is expected to have potential applications in the fields of optical manipulation and optogenetics.展开更多
Independent manipulation of orthogonal circularly polarized wavefronts is one of the important goals for metaoptics,and chiral nanophotonics is one of the crucial approaches.In this article,we propose a new scheme for...Independent manipulation of orthogonal circularly polarized wavefronts is one of the important goals for metaoptics,and chiral nanophotonics is one of the crucial approaches.In this article,we propose a new scheme for spin-dependent terahertz wavefront shaping based on chiral metasurfaces,which involves a hybrid design of the propagation phase,chirality induced phase,and Pancharatnam-Berry phase in all-silicon meta-atoms.A controllable linear polarization conversion effect in the transmitted wave is obtained via breaking the mirror symmetry and preserving the C_(2)symmetry of the resonator,which causes a different form of the Jones matrix.By simultaneously adjusting the in-plane geometric dimensions and azimuth angle of chiral units,and utilizing the evolution characteristics of circularly polarized components in parameter space and polarization space,spin-dependent phase responses have been observed.We provide the main theoretical analysis and demonstrate the functional design of circularly polarized multiplexed beam deflection or vortex beam generation,through the expected simulation and experimental results near the operating frequency of 0.6 THz.Our results may enrich the design of terahertz polarization-multiplexed devices.展开更多
In this Letter,we propose and experimentally demonstrate a lens-free wavefront shaping method that utilizes synchronized signal block beam alignment and a genetic algorithm(SSBGA)for a diffuse non-line-of-sight(NLOS)v...In this Letter,we propose and experimentally demonstrate a lens-free wavefront shaping method that utilizes synchronized signal block beam alignment and a genetic algorithm(SSBGA)for a diffuse non-line-of-sight(NLOS)visible light communication(VLC)system.The proposed method effectively controls the position and mobility of visible light beams by partitioning spatial light modulator pixels and manipulating beams to converge at distinct spatial positions,thereby enhancing wavefront shaping efficiency,which achieves a significant 23.9 dB optical power enhancement at+2 mm offset,surpassing the lens-based continuous sequence(CS)scheme by 21.7 dB.At+40°angle,the improvement reaches up to 11.8 dB and 16.8 dB compared to the results with and without lens-based CS,respectively.A maximum rate of 5.16 Gbps is successfully achieved using bit-power loading discrete multi-tone(DMT)modulation and the proposed SSBGA in an NLOS VLC system,which outperforms the lens-based CS by 1.07 Gbps and obtains a power saving of 55.6%during the transmission at4 Gbps.To the best of our knowledge,this is the first time that high-speed communication has been realized in an NLOS VLC system without a lens.展开更多
Light passing through a subwavelength hole in an opaque plate is a fundamental concern in both optical science and applications.Using both simulations and experiments,we show that,when a subwavelength hole in a silver...Light passing through a subwavelength hole in an opaque plate is a fundamental concern in both optical science and applications.Using both simulations and experiments,we show that,when a subwavelength hole in a silver thin film is surrounded by well-designed patterns of grooves,the wavefront of the infrared light through it can be shaped into a preset complicated pattern such as a Latin letter‘L’or‘O’at a given position instead of being diffracted in all directions.The design is created via the surface-wave-holography method,which allows direct determination of the surface plasmonic structure for a given wavefront-engineering functionality without the need to solve complex inverse problems.The results will deepen current understanding of this enduring issue and will find applications in many fields such as wave manipulation and sensing.展开更多
Orbital angular momentum(OAM)is a fundamental physical characteristic to describe laser fields with a spiral phase structure.Vortex beams carrying OAMs have attracted more and more attention in recent years.However,th...Orbital angular momentum(OAM)is a fundamental physical characteristic to describe laser fields with a spiral phase structure.Vortex beams carrying OAMs have attracted more and more attention in recent years.However,the wavefront of OAM light would be destroyed when it passes through scattering media.Here,based on the feedback-based wavefront shaping method,we reconstitute OAM wavefronts behind strongly scattering media.The intensity of light with desired OAM states is enhanced to 150 times.This study provides a method to manipulate OAMs of scattered light and is of great significance for OAM optical communication and imaging to overcome complex environment interference.展开更多
We demonstrate a new concept for reconfigurable nanophotonic devices exploiting ultrafast nonlinear control of shaped wavefronts in a multimode nanomaterial consisting of semiconductor nanowires.Femtosecond pulsed las...We demonstrate a new concept for reconfigurable nanophotonic devices exploiting ultrafast nonlinear control of shaped wavefronts in a multimode nanomaterial consisting of semiconductor nanowires.Femtosecond pulsed laser excitation of the nanowire mat is shown to provide an efficient nonlinear mechanism to control both destructive and constructive interference in a shaped wavefront.Modulations of up to 63%are induced by optical pumping,due to a combination of multimode dephasing and induced transient absorption.We show that part of the nonlinear phase dynamics can be inverted to provide a dynamical revival of the wavefront into an optimized spot with up to 18%increase of the peak to background ratio caused by pulsed laser excitation.The concepts of multimode nonlinear switching demonstrated here are generally extendable to other photonic and plasmonic systems and enable new avenues for ultrafast and reconfigurable nanophotonic devices.展开更多
We demonstrate a modified particle swarm optimization(PSO) algorithm to effectively shape the incident light with strong robustness and short optimization time. The performance of the modified PSO algorithm and geneti...We demonstrate a modified particle swarm optimization(PSO) algorithm to effectively shape the incident light with strong robustness and short optimization time. The performance of the modified PSO algorithm and genetic algorithm(GA) is numerically simulated. Then, using a high speed digital micromirror device, we carry out light focusing experiments with the modified PSO algorithm and GA. The experimental results show that the modified PSO algorithm has greater robustness and faster convergence speed than GA. This modified PSO algorithm has great application prospects in optical focusing and imaging inside in vivo biological tissue, which possesses a complicated background.展开更多
Object imaging beyond the direct line of sight is significant for applications in robotic vision,remote sensing,autonomous driving,and many other areas.Reconstruction of a non-line-of-sight(NLOS)screen is a complex in...Object imaging beyond the direct line of sight is significant for applications in robotic vision,remote sensing,autonomous driving,and many other areas.Reconstruction of a non-line-of-sight(NLOS)screen is a complex inverse problem that comes with ultrafast time-resolved imager requirements and substantial computational demands to extract information from the multi-bounce scattered light.Consequently,the echo signal always suffers from serious deterioration in both intensity and shape,leading to limited resolution and image contrast.Here,we propose a concept of vectorial digitelligent optics for high-resolution NLOS imaging to cancel the wall’s scattering and refocus the light onto hidden targets for enhanced echo.In this approach,the polarization and wavefront of the laser spot are intelligently optimized via a feedback algorithm to form a near-perfect focusing pattern through a random scattering wall.By raster scanning the focusing spot across the object’s surface within the optical-memory-effect range of the wall,we obtain nearly diffraction-limited NLOS imaging with an enhanced signal-to-noise ratio.Our experimental results demonstrate a resolution of 0.40 mm at a distance of 0.35 m,reaching the diffraction limit of the system.Furthermore,we demonstrate that the proposed method is feasible for various complex NLOS scenarios.Our methods may open an avenue for active imaging,communication,and laser wireless power transfer.展开更多
This work introduces special states for light in multimode fibers featuring strongly enhanced or reduced correlations be-tween output fields in the presence of environmental temperature fluctuations.Using experimental...This work introduces special states for light in multimode fibers featuring strongly enhanced or reduced correlations be-tween output fields in the presence of environmental temperature fluctuations.Using experimentally measured multi-tem-perature transmission matrix,a set of temperature principal modes that exhibit resilience to disturbances caused by tem-perature fluctuations can be generated.Reversing this concept also allows the construction of temperature anti-principal modes,with output profiles more susceptible to temperature influences than the unmodulated wavefront.Despite changes in the length of the multimode fiber within the temperature-fluctuating region,the proposed approach remains capable of robustly controlling the temperature response within the fiber.To illustrate the practicality of the proposed spe-cial state,a learning-empowered fiber specklegram temperature sensor based on temperature anti-principal mode sensi-tization is proposed.This sensor exhibits outstanding superiority over traditional approaches in terms of resolution and accuracy.These novel states are anticipated to have wide-ranging applications in fiber communication,sensing,imaging,and spectroscopy,and serve as a source of inspiration for the discovery of other novel states.展开更多
The spectral memory effect in scattering media is crucial for applications that employ broadband illumination,as it dictates the available spectral range from independent scattering responses.Previous studies mainly c...The spectral memory effect in scattering media is crucial for applications that employ broadband illumination,as it dictates the available spectral range from independent scattering responses.Previous studies mainly considered a passive result with the average impact of the scattering medium,whereas it is vital to actively enhance or suppress this effect for applications concerned with large spectral range or fine resolution.We construct an analytical model by integrating the concepts of wave-based interference and photon-based propagation,which manifests a potential physical image for active manipulation by utilizing scattering eigenchannels.Our theoretical predictions indicate that the spectral memory effect is enhanced using high-transmission eigenchannels while it is suppressed using low-transmission eigenchannels.These predictions are supported by finite-difference time-domain simulations and experiments,demonstrating that the spectral memory effect’s range can be actively manipulated.Quantitatively,the experiments achieved variations in enhancement and suppression that exceeded threefold(∼3.27).We clarify the underlying principles of the spectral memory effect in scattering media and demonstrate active manipulation of multispectral scattering processes.展开更多
Optical endoscopy has become an essential diagnostic and therapeutic approach in modern biomedicine for directly observing organs and tissues deep inside the human body,enabling non-invasive,rapid diagnosis and treatm...Optical endoscopy has become an essential diagnostic and therapeutic approach in modern biomedicine for directly observing organs and tissues deep inside the human body,enabling non-invasive,rapid diagnosis and treatment.Optical fiber endoscopy is highly competitive among various endoscopic imaging techniques due to its high flexibility,compact structure,excellent resolution,and resistance to electromagnetic interference.Over the past decade,endoscopes based on a single multimode optical fiber(MMF)have attracted widespread research interest due to their potential to significantly reduce the footprint of optical fiber endoscopes and enhance imaging capabilities.In comparison with other imaging principles of MMF endoscopes,the scanning imaging method based on the wavefront shaping technique is highly developed and provides benefits including excellent imaging contrast,broad applicability to complex imaging scenarios,and good compatibility with various well-established scanning imaging modalities.In this review,various technical routes to achieve light focusing through MMF and procedures to conduct the scanning imaging of MMF endoscopes are introduced.The advancements in imaging performance enhancements,integrations of various imaging modalities with MMF scanning endoscopes,and applications are summarized.Challenges specific to this endoscopic imaging technology are analyzed,and potential remedies and avenues for future developments are discussed.展开更多
Coherent optical control within or through scattering media via wavefront shaping has seen broad applications since its invention around 2007.Wavefront shaping is aimed at overcoming the strong scattering,featured by ...Coherent optical control within or through scattering media via wavefront shaping has seen broad applications since its invention around 2007.Wavefront shaping is aimed at overcoming the strong scattering,featured by random interference,namely speckle patterns.This randomness occurs due to the refractive index inhomogeneity in complex media like biological tissue or the modal dispersion in multimode fiber,yet this randomness is actually deterministic and potentially can be time reversal or precompensated.Various wavefront shaping approaches,such as optical phase conjugation,iterative optimization,and transmission matrix measurement,have been developed to generate tight and intense optical delivery or high-resolution image of an optical object behind or within a scattering medium.The performance of these modula-tions,however,is far from satisfaction.Most recently,artifcial intelligence has brought new inspirations to this field,providing exciting hopes to tackle the challenges by mapping the input and output optical patterns and building a neuron network that inherently links them.In this paper,we survey the developments to date on this topic and briefly discuss our views on how to harness machine learning(deep learning in particular)for further advancements in the field.展开更多
Transmission matrix(TM)allows light control through complex media,such as multimode fibers(MMFs),gaining great attention in areas,such as biophotonics,over the past decade.Efforts have been taken to retrieve a complex...Transmission matrix(TM)allows light control through complex media,such as multimode fibers(MMFs),gaining great attention in areas,such as biophotonics,over the past decade.Efforts have been taken to retrieve a complex-valued TM directly from intensity measurements with several representative phase-retrieval algorithms,which still see limitations of slow or suboptimum recovery,especially under noisy environments.Here,we propose a modified nonconvex optimization approach.Through numerical evaluations,it shows that the optimum focusing efficiency is approached with less running time or sampling ratio.The comparative tests under different signal-to-noise levels further indicate its improved robustness.Experimentally,the superior focusing performance of our algorithm is collectively validated by single-and multispot focusing;especially with a sampling ratio of 8,it achieves a 93.6%efficiency of the gold-standard holography method.Based on the recovered TM,image transmission through an MMF is realized with high fidelity.Due to parallel operation and GPU acceleration,our nonconvex approach retrieves a 8685×1024 TM(sampling ratio is 8)with 42.3 s on average on a regular computer.The proposed method provides optimum efficiency and fast execution for TM retrieval that avoids the need for an external reference beam,which will facilitate applications of deep-tissue optical imaging,manipulation,and treatment.展开更多
To increase the quantum efficiency （QE） of a copper photocathode and reduce the thermal emit- tance of an electron beam, a drive laser with oblique incidence was adopted in a BNL type photocathode rf gun. The disadv...To increase the quantum efficiency （QE） of a copper photocathode and reduce the thermal emit- tance of an electron beam, a drive laser with oblique incidence was adopted in a BNL type photocathode rf gun. The disadvantageous effects on the beam quality caused by oblique incidence were analyzed qualitatively. A simple way to solve the problems through wavefront shaping was introduced and the beam quality was improved.展开更多
Light-based additive manufacturing holds great potential in the field of bioprinting due to its exceptional spatial resolution,enabling the reconstruction of intricate tissue structures.However,printing through biolog...Light-based additive manufacturing holds great potential in the field of bioprinting due to its exceptional spatial resolution,enabling the reconstruction of intricate tissue structures.However,printing through biological tissues is severely limited due to the strong optical scattering within the tissues.The propagation of light is scrambled to form random speckle patterns,making it impossible to print features at the diffraction-limited size with conventional printing approaches.The poor tissue penetration depth of ultra-violet or blue light,which is commonly used to trigger photopolymerization,further limits the fabrication of high cell-density tissue constructs.Recently,several strategies based on wavefront shaping have been developed to manipulate the light and refocus it inside scattering media to a diffraction-limited spot.In this study,we present a high-resolution additive manufacturing technique using upconversion nanoparticles and a wavefront shaping method that does not require measurement from an invasive detector,i.e.,it is a non-invasive technique.Upconversion nanoparticles convert near-infrared light to ultraviolet and visible light.The ultraviolet light serves as a light source for photopolymerization and the visible light as a guide star for digital light shaping.The incident light pattern is manipulated using the feedback information of the guide star to focus light through the tissue.In this way,we experimentally demonstrate that near-infrared light can be non-invasively focused through a strongly scattering medium.By exploiting the optical memory effect,we further demonstrate micro-meter resolution additive manufacturing through highly scattering media such as a 300-μm-thick chicken breast.This study provides a concept of high-resolution additive manufacturing through turbid media with potential application in tissue engineering.展开更多
In vivo microscopic imaging inside a biological lumen such as the gastrointestinal tract,respiratory airways,or within blood vessels has faced significant technological challenges for decades.A promising candidate tec...In vivo microscopic imaging inside a biological lumen such as the gastrointestinal tract,respiratory airways,or within blood vessels has faced significant technological challenges for decades.A promising candidate technology is the multimode fiber(MMF)endoscope,which enables minimally invasive diagnostics at a resolution reaching the cellular level.However,for in vivo imaging applications deep inside a biological lumen,sample-induced aberrations and the dynamic dispersion in the MMF make the MMF endoscope a chaotic system with many unknowns,where multiple minor fluctuations can couple and compound into intractable problems.We introduce a dynamically encoding,cascaded,optical,and ultrathin polychromatic light-field endoscopy(DECOUPLE)to tackle this challenge.DECOUPLE includes an adaptive aberration correction that can accurately track and control MMF behavior in the spatial-frequency domain to compensate for chaos introduced during complex dynamic imaging processes.We demonstrate the flexibility and practicality of DECOUPLE for noninvasive volumetric imaging in two colors for light passing through various highly aberrating samples including 120-μm-thick onion epidermal slices and 80-μm-thick layers of fat emulsions.To summarize,we represent a significant step toward practical in vivo imaging deep within biological tissue.展开更多
文摘Feedback-based wavefront shaping focuses light through scattering media by employing phase optimization algorithms.Genetic algorithms(GAs),inspired by the process of natural selection,are well suited for phase optimization in wavelfront shaping problems.In 2012,Conkey et al.first introduced a GA into feedback-based wavefront shaping to find the optimum phase map.Since then,due to its siuperior performance in noisy environment,the GA has been widely adopted by lots of implementations.However,there have been limited studies discussing and optimizing the detailed procedures of the GA.To fill this blank,in this study,we performed a thorough study on the performance of the GA for focusing light through scattering media.Using numerical tools,we evaluated certain procedures that can be potentially improved and provided guidance on how to choose certain parameters appropriately.This study is beneficial in improving the performance of wavefront shaping systems with GAs.
基金supported by the Shenzhen Science and Technology Innovation Commission(No.JCYJ20170818104421564)the Hong Kong Innovation and Technology Commission(No.ITS/022/18)+1 种基金the Hong Kong Research Grant Council(No.25204416)the National Natural Science Foundation of China(Nos.81671726 and 81627805).
文摘Wavefront shaping(WFS)techniques have been used as a powerful tool to control light propagation in complex media,including multimode fibers.In this paper,we propose a new application of WFS for multimode fber-based sensors.The use of a single multimode fiber alone,without any special fabrication,as a sensor based on the light intensity variations is not an easy task.The twist effect on multimode fiber is used as an example herein.Experimental results show that light intensity through the multimode fiber shows no direct relationship with the twist angle,but the correlation coefficient(CC)of speckle patterns does.Moreover,if WFS is applied to transform the spatially seemingly random light pattern at the exit of the multimode fiber into an optical focus.The focal pattern correlation and intensity both can serve to gauge the twist angle,with doubled measurement range and allowance of using a fast point detector to provide the feedback.With further development,WFS may find potentials to facilitate the development of multimode fber-based sensors in a variety of scenarios.
文摘By manipulating the phase map of a wavefront of light using a spatial light modulator,the scattered light can be sharply focused on a specific target.Several iterative optimization algo-rithrns for obtaining the optimumn phase map have been explored.However,there has not been a comparative study on the performance of these algorithms.In this paper,six optimization algorithms for wavefront shaping inchuding continuous sequential,partitioning algorithm,transmission matrix estimation method,particle swarm optimization,genetic algorithm(GA),and simulated annealing(SA)are discussed and compared based on their efficiency when introduced with various measurement noise levels.
基金supported by the National Research Foundation of Korea(Nos.2016R1C1B201530 and 2017M3C7A1044966)the Agency for Defense Development(UD170075FD)the TJ Park Foundation.
文摘Despite the unique advantages of optical microscopy for molecular specific high resolution imaging of living structure in both space and time,curent applications are mostly limited to research settings.This is due to the aberrations and multiple scattering that is induced by the inhomogeneous refractive boundaries that are inherent to biological systems.However,recent developments in adaptive optics and wavefront shaping have shown that high resolution optical imaging is not fundamentally limited only to the observation of single cells,but can be significantly enhanced to realize deep tissue imaging.To provide insight into how these two closely related fields can expand the limits of bio imaging,we review the recent progresses in their performance and applicable range of studies as well as potential future research directions to push the limits of deep tissuse imnaging.
基金Project supported by the Natural Science Foundation of Beijing Municipality,China(Grant No.7182091)。
文摘We use feedback wavefront shaping technology to realize the multi-point uniform light focusing in three-dimensional(3D) space through scattering media only by loading the optimal mask once.General 3D spatial focusing needs to load the optimal mask multiple times to realize the spatial movement of the focal point and the uniformity of multi-point focusing cannot be guaranteed.First,we investigate the effects of speckle axial correlation and different axial distances on 3D spatial multi-point uniform focusing and propose possible solutions.Then we use our developed non-dominated sorting genetic algorithm suitable for 3D spatial focusing(S-NSGA) to verify the experiment of multi-point focusing in 3D space.This research is expected to have potential applications in the fields of optical manipulation and optogenetics.
基金National Natural Science Foundation of China(12404484)Science and Technology Department of Sichuan Province(2025ZNSFSC0846,2025ZNSFSC0847,2022Z091,2023ZYD0175)+1 种基金Scientific Research Foundation of Chengdu University of Information Technology(KYTZ202245)Sichuan Meteorological Optoelectronic Sensor Technology and Application Engineering Research Center(2024GCZX001)。
文摘Independent manipulation of orthogonal circularly polarized wavefronts is one of the important goals for metaoptics,and chiral nanophotonics is one of the crucial approaches.In this article,we propose a new scheme for spin-dependent terahertz wavefront shaping based on chiral metasurfaces,which involves a hybrid design of the propagation phase,chirality induced phase,and Pancharatnam-Berry phase in all-silicon meta-atoms.A controllable linear polarization conversion effect in the transmitted wave is obtained via breaking the mirror symmetry and preserving the C_(2)symmetry of the resonator,which causes a different form of the Jones matrix.By simultaneously adjusting the in-plane geometric dimensions and azimuth angle of chiral units,and utilizing the evolution characteristics of circularly polarized components in parameter space and polarization space,spin-dependent phase responses have been observed.We provide the main theoretical analysis and demonstrate the functional design of circularly polarized multiplexed beam deflection or vortex beam generation,through the expected simulation and experimental results near the operating frequency of 0.6 THz.Our results may enrich the design of terahertz polarization-multiplexed devices.
基金supported by the National Key Research and Development Program of China(No.2022YFB2802803)the National Natural Science Foundation of China(Nos.61925104,62031011,and 62201157)。
文摘In this Letter,we propose and experimentally demonstrate a lens-free wavefront shaping method that utilizes synchronized signal block beam alignment and a genetic algorithm(SSBGA)for a diffuse non-line-of-sight(NLOS)visible light communication(VLC)system.The proposed method effectively controls the position and mobility of visible light beams by partitioning spatial light modulator pixels and manipulating beams to converge at distinct spatial positions,thereby enhancing wavefront shaping efficiency,which achieves a significant 23.9 dB optical power enhancement at+2 mm offset,surpassing the lens-based continuous sequence(CS)scheme by 21.7 dB.At+40°angle,the improvement reaches up to 11.8 dB and 16.8 dB compared to the results with and without lens-based CS,respectively.A maximum rate of 5.16 Gbps is successfully achieved using bit-power loading discrete multi-tone(DMT)modulation and the proposed SSBGA in an NLOS VLC system,which outperforms the lens-based CS by 1.07 Gbps and obtains a power saving of 55.6%during the transmission at4 Gbps.To the best of our knowledge,this is the first time that high-speed communication has been realized in an NLOS VLC system without a lens.
基金This work was supported by the National Basic Research Foundation of China under grant no.2011CB922002 and Knowledge Innovation Program of the Chinese Academy of Sciences(No.Y1V2013L11).
文摘Light passing through a subwavelength hole in an opaque plate is a fundamental concern in both optical science and applications.Using both simulations and experiments,we show that,when a subwavelength hole in a silver thin film is surrounded by well-designed patterns of grooves,the wavefront of the infrared light through it can be shaped into a preset complicated pattern such as a Latin letter‘L’or‘O’at a given position instead of being diffracted in all directions.The design is created via the surface-wave-holography method,which allows direct determination of the surface plasmonic structure for a given wavefront-engineering functionality without the need to solve complex inverse problems.The results will deepen current understanding of this enduring issue and will find applications in many fields such as wave manipulation and sensing.
基金supported in part by the National Natural Science Foundation of China(NSFC)(Nos.11734011,62022058,12074252,and 12004245)the National Key R&D Program of China(Nos.2017YFA0303701 and 2018YFA0306301)+2 种基金the Shanghai Municipal Science and Technology Major Project(No.2019SHZDZX01)the Shanghai Rising-Star Program(No.20QA1405400)the Shandong Quancheng Scholarship(No.00242019024)。
文摘Orbital angular momentum(OAM)is a fundamental physical characteristic to describe laser fields with a spiral phase structure.Vortex beams carrying OAMs have attracted more and more attention in recent years.However,the wavefront of OAM light would be destroyed when it passes through scattering media.Here,based on the feedback-based wavefront shaping method,we reconstitute OAM wavefronts behind strongly scattering media.The intensity of light with desired OAM states is enhanced to 150 times.This study provides a method to manipulate OAMs of scattered light and is of great significance for OAM optical communication and imaging to overcome complex environment interference.
基金The authors thank E Bakkers from Eindhoven University of Technology for providing the nanowire sample.OLM and RB acknowledge financial support from EPSRC through grant EP/J016918/1.
文摘We demonstrate a new concept for reconfigurable nanophotonic devices exploiting ultrafast nonlinear control of shaped wavefronts in a multimode nanomaterial consisting of semiconductor nanowires.Femtosecond pulsed laser excitation of the nanowire mat is shown to provide an efficient nonlinear mechanism to control both destructive and constructive interference in a shaped wavefront.Modulations of up to 63%are induced by optical pumping,due to a combination of multimode dephasing and induced transient absorption.We show that part of the nonlinear phase dynamics can be inverted to provide a dynamical revival of the wavefront into an optimized spot with up to 18%increase of the peak to background ratio caused by pulsed laser excitation.The concepts of multimode nonlinear switching demonstrated here are generally extendable to other photonic and plasmonic systems and enable new avenues for ultrafast and reconfigurable nanophotonic devices.
基金Supported by the National Key Research and Development Program of China under Grant No 2017YFB1104500the Natural Science Foundation of Beijing under Grant No 7182091,the National Natural Science Foundation of China under Grant No 21627813the Fundamental Research Funds for the Central Universities under Grant No PYBZ1801
文摘We demonstrate a modified particle swarm optimization(PSO) algorithm to effectively shape the incident light with strong robustness and short optimization time. The performance of the modified PSO algorithm and genetic algorithm(GA) is numerically simulated. Then, using a high speed digital micromirror device, we carry out light focusing experiments with the modified PSO algorithm and GA. The experimental results show that the modified PSO algorithm has greater robustness and faster convergence speed than GA. This modified PSO algorithm has great application prospects in optical focusing and imaging inside in vivo biological tissue, which possesses a complicated background.
基金supported by the National Key Research and Development Program of China(2023YFB2805800 and 2021YFA1401003)the National Natural Science Foundation of China(62222513).
文摘Object imaging beyond the direct line of sight is significant for applications in robotic vision,remote sensing,autonomous driving,and many other areas.Reconstruction of a non-line-of-sight(NLOS)screen is a complex inverse problem that comes with ultrafast time-resolved imager requirements and substantial computational demands to extract information from the multi-bounce scattered light.Consequently,the echo signal always suffers from serious deterioration in both intensity and shape,leading to limited resolution and image contrast.Here,we propose a concept of vectorial digitelligent optics for high-resolution NLOS imaging to cancel the wall’s scattering and refocus the light onto hidden targets for enhanced echo.In this approach,the polarization and wavefront of the laser spot are intelligently optimized via a feedback algorithm to form a near-perfect focusing pattern through a random scattering wall.By raster scanning the focusing spot across the object’s surface within the optical-memory-effect range of the wall,we obtain nearly diffraction-limited NLOS imaging with an enhanced signal-to-noise ratio.Our experimental results demonstrate a resolution of 0.40 mm at a distance of 0.35 m,reaching the diffraction limit of the system.Furthermore,we demonstrate that the proposed method is feasible for various complex NLOS scenarios.Our methods may open an avenue for active imaging,communication,and laser wireless power transfer.
基金financial supports from the National Natural Science Foundation of China (62075132 and 92050202)Natural Science Foundation of Shanghai (22ZR1443100)
文摘This work introduces special states for light in multimode fibers featuring strongly enhanced or reduced correlations be-tween output fields in the presence of environmental temperature fluctuations.Using experimentally measured multi-tem-perature transmission matrix,a set of temperature principal modes that exhibit resilience to disturbances caused by tem-perature fluctuations can be generated.Reversing this concept also allows the construction of temperature anti-principal modes,with output profiles more susceptible to temperature influences than the unmodulated wavefront.Despite changes in the length of the multimode fiber within the temperature-fluctuating region,the proposed approach remains capable of robustly controlling the temperature response within the fiber.To illustrate the practicality of the proposed spe-cial state,a learning-empowered fiber specklegram temperature sensor based on temperature anti-principal mode sensi-tization is proposed.This sensor exhibits outstanding superiority over traditional approaches in terms of resolution and accuracy.These novel states are anticipated to have wide-ranging applications in fiber communication,sensing,imaging,and spectroscopy,and serve as a source of inspiration for the discovery of other novel states.
基金supported by the National Natural Science Foundation of China(Grant Nos.12325408,92150102,62205302,92150301,12274129,12074121,62105101,62175066,12274139,and 12404380)the Fundamental and Applied Basic Research Project of Guangzhou(Grant No.2024A04J2001)the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2024B1515020051 and 2023A1515110742).
文摘The spectral memory effect in scattering media is crucial for applications that employ broadband illumination,as it dictates the available spectral range from independent scattering responses.Previous studies mainly considered a passive result with the average impact of the scattering medium,whereas it is vital to actively enhance or suppress this effect for applications concerned with large spectral range or fine resolution.We construct an analytical model by integrating the concepts of wave-based interference and photon-based propagation,which manifests a potential physical image for active manipulation by utilizing scattering eigenchannels.Our theoretical predictions indicate that the spectral memory effect is enhanced using high-transmission eigenchannels while it is suppressed using low-transmission eigenchannels.These predictions are supported by finite-difference time-domain simulations and experiments,demonstrating that the spectral memory effect’s range can be actively manipulated.Quantitatively,the experiments achieved variations in enhancement and suppression that exceeded threefold(∼3.27).We clarify the underlying principles of the spectral memory effect in scattering media and demonstrate active manipulation of multispectral scattering processes.
基金supported by National Natural Science Foundation of China(62135007 and 61925502).
文摘Optical endoscopy has become an essential diagnostic and therapeutic approach in modern biomedicine for directly observing organs and tissues deep inside the human body,enabling non-invasive,rapid diagnosis and treatment.Optical fiber endoscopy is highly competitive among various endoscopic imaging techniques due to its high flexibility,compact structure,excellent resolution,and resistance to electromagnetic interference.Over the past decade,endoscopes based on a single multimode optical fiber(MMF)have attracted widespread research interest due to their potential to significantly reduce the footprint of optical fiber endoscopes and enhance imaging capabilities.In comparison with other imaging principles of MMF endoscopes,the scanning imaging method based on the wavefront shaping technique is highly developed and provides benefits including excellent imaging contrast,broad applicability to complex imaging scenarios,and good compatibility with various well-established scanning imaging modalities.In this review,various technical routes to achieve light focusing through MMF and procedures to conduct the scanning imaging of MMF endoscopes are introduced.The advancements in imaging performance enhancements,integrations of various imaging modalities with MMF scanning endoscopes,and applications are summarized.Challenges specific to this endoscopic imaging technology are analyzed,and potential remedies and avenues for future developments are discussed.
基金supported by the National Natural Science Foundation of China(Nos.81671726 and 81627805)the Hong Kong Research Grant Council(No.25204416)+1 种基金the Shenzhen Science and Technology Innovation Commission(No.JCYJ20170818104421564)the Hong Kong Innovation and Technology Commission(No.ITS/022/18).
文摘Coherent optical control within or through scattering media via wavefront shaping has seen broad applications since its invention around 2007.Wavefront shaping is aimed at overcoming the strong scattering,featured by random interference,namely speckle patterns.This randomness occurs due to the refractive index inhomogeneity in complex media like biological tissue or the modal dispersion in multimode fiber,yet this randomness is actually deterministic and potentially can be time reversal or precompensated.Various wavefront shaping approaches,such as optical phase conjugation,iterative optimization,and transmission matrix measurement,have been developed to generate tight and intense optical delivery or high-resolution image of an optical object behind or within a scattering medium.The performance of these modula-tions,however,is far from satisfaction.Most recently,artifcial intelligence has brought new inspirations to this field,providing exciting hopes to tackle the challenges by mapping the input and output optical patterns and building a neuron network that inherently links them.In this paper,we survey the developments to date on this topic and briefly discuss our views on how to harness machine learning(deep learning in particular)for further advancements in the field.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant No.81930048)the Hong Kong Innovation and Technology Commission(Grant Nos.GHP/043/19SZ and GHP/044/19GD)+3 种基金the Hong Kong Research Grant Council(Grant Nos.15217721,R5029-19 and C7074-21GF)the Guangdong Science and Technology Commission(Grant No.2019BT02X105)the Shenzhen Science and Technology Innovation Commission(Grant No.JCYJ20220818100202005)the Hong Kong Polytechnic University(Grant Nos.P0038180,P0039517,P0043485 and P0045762).
文摘Transmission matrix(TM)allows light control through complex media,such as multimode fibers(MMFs),gaining great attention in areas,such as biophotonics,over the past decade.Efforts have been taken to retrieve a complex-valued TM directly from intensity measurements with several representative phase-retrieval algorithms,which still see limitations of slow or suboptimum recovery,especially under noisy environments.Here,we propose a modified nonconvex optimization approach.Through numerical evaluations,it shows that the optimum focusing efficiency is approached with less running time or sampling ratio.The comparative tests under different signal-to-noise levels further indicate its improved robustness.Experimentally,the superior focusing performance of our algorithm is collectively validated by single-and multispot focusing;especially with a sampling ratio of 8,it achieves a 93.6%efficiency of the gold-standard holography method.Based on the recovered TM,image transmission through an MMF is realized with high fidelity.Due to parallel operation and GPU acceleration,our nonconvex approach retrieves a 8685×1024 TM(sampling ratio is 8)with 42.3 s on average on a regular computer.The proposed method provides optimum efficiency and fast execution for TM retrieval that avoids the need for an external reference beam,which will facilitate applications of deep-tissue optical imaging,manipulation,and treatment.
基金Supported by Science Foundation of Ministry of Education of China ('985 project':173123200402002)
文摘To increase the quantum efficiency （QE） of a copper photocathode and reduce the thermal emit- tance of an electron beam, a drive laser with oblique incidence was adopted in a BNL type photocathode rf gun. The disadvantageous effects on the beam quality caused by oblique incidence were analyzed qualitatively. A simple way to solve the problems through wavefront shaping was introduced and the beam quality was improved.
基金funding from the Swiss National Science Foundation under project number 196971-“Light based Volumetric printing in scattering resins.”。
文摘Light-based additive manufacturing holds great potential in the field of bioprinting due to its exceptional spatial resolution,enabling the reconstruction of intricate tissue structures.However,printing through biological tissues is severely limited due to the strong optical scattering within the tissues.The propagation of light is scrambled to form random speckle patterns,making it impossible to print features at the diffraction-limited size with conventional printing approaches.The poor tissue penetration depth of ultra-violet or blue light,which is commonly used to trigger photopolymerization,further limits the fabrication of high cell-density tissue constructs.Recently,several strategies based on wavefront shaping have been developed to manipulate the light and refocus it inside scattering media to a diffraction-limited spot.In this study,we present a high-resolution additive manufacturing technique using upconversion nanoparticles and a wavefront shaping method that does not require measurement from an invasive detector,i.e.,it is a non-invasive technique.Upconversion nanoparticles convert near-infrared light to ultraviolet and visible light.The ultraviolet light serves as a light source for photopolymerization and the visible light as a guide star for digital light shaping.The incident light pattern is manipulated using the feedback information of the guide star to focus light through the tissue.In this way,we experimentally demonstrate that near-infrared light can be non-invasively focused through a strongly scattering medium.By exploiting the optical memory effect,we further demonstrate micro-meter resolution additive manufacturing through highly scattering media such as a 300-μm-thick chicken breast.This study provides a concept of high-resolution additive manufacturing through turbid media with potential application in tissue engineering.
基金Financial support was provided by the National Natural Science Foundation of China(Grant Nos.T2293751,T2293750,62405278,6240030458,62020106002,61735017,and 92250304)National Key Basic Research Program of China(Grant No.2021YFC2401403)+2 种基金National Key Research and Development Program of China(Grant Nos.2024YFF1206700 and 2024YFF1206705)Major Scientific Research Project of Zhejiang Laboratory(Grant No.2019MC0AD02)the Zhejiang University Education Foundation Global Partnership Fund.
文摘In vivo microscopic imaging inside a biological lumen such as the gastrointestinal tract,respiratory airways,or within blood vessels has faced significant technological challenges for decades.A promising candidate technology is the multimode fiber(MMF)endoscope,which enables minimally invasive diagnostics at a resolution reaching the cellular level.However,for in vivo imaging applications deep inside a biological lumen,sample-induced aberrations and the dynamic dispersion in the MMF make the MMF endoscope a chaotic system with many unknowns,where multiple minor fluctuations can couple and compound into intractable problems.We introduce a dynamically encoding,cascaded,optical,and ultrathin polychromatic light-field endoscopy(DECOUPLE)to tackle this challenge.DECOUPLE includes an adaptive aberration correction that can accurately track and control MMF behavior in the spatial-frequency domain to compensate for chaos introduced during complex dynamic imaging processes.We demonstrate the flexibility and practicality of DECOUPLE for noninvasive volumetric imaging in two colors for light passing through various highly aberrating samples including 120-μm-thick onion epidermal slices and 80-μm-thick layers of fat emulsions.To summarize,we represent a significant step toward practical in vivo imaging deep within biological tissue.
