Physics-data-driven intelligent optimization for large-aperture metalenses

Metalenses have gained significant attention and have been widely utilized in optical systems for focusing and imaging,owing to their lightweight,high-integration,and exceptional-flexibility capabilities.Traditional design methods neglect the coupling effect between adjacent meta-atoms,thus harming the practical performance of meta-devices.The existing physical/data-driven optimization algorithms can solve the above problems,but bring significant time costs or require a large number of data-sets.Here,we propose a physics-data-driven method employing an“intelligent optimizer”that enables us to adaptively modify the sizes of the meta-atom according to the sizes of its surrounding ones.The implementation of such a scheme effectively mitigates the undesired impact of local lattice coupling,and the proposed network model works well on thousands of data-sets with a validation loss of 3×10^(−3).Based on the“intelligent optimizer”,a 1-cm-diameter metalens is designed within 3 hours,and the experimental results show that the 1-mm-diameter metalens has a relative focusing efficiency of 93.4%(compared to the ideal focusing efficiency)and a Strehl ratio of 0.94.Compared to previous inverse design method,our method significantly boosts designing efficiency with five orders of magnitude reduction in time.More generally,it may set a new paradigm for devising large-aperture meta-devices.

Improved spatiotemporal resolution of anti-scattering super-resolution label-free microscopy via synthetic wave 3D metalens imaging

Super-resolution(SR)microscopy has dramatically enhanced our understanding of biological processes.However,scattering media in thick specimens severely limits the spatial resolution,often rendering the images unclear or indistinguishable.Additionally,live-cell imaging faces challenges in achieving high temporal resolution for fast-moving subcellular structures.Here,we present the principles of a synthetic wave microscopy(SWM)to extract three-dimensional information from thick unlabeled specimens,where photobleaching and phototoxicity are avoided.SWM exploits multiple-wave interferometry to reveal the specimen’s phase information in the area of interest,which is not affected by the scattering media in the optical path.SWM achieves~0.42λ/NA resolution at an imaging speed of up to 106 pixels/s.SWM proves better temporal resolution and sensitivity than the most conventional microscopes currently available while maintaining exceptional SR and anti-scattering capabilities.Penetrating through the scattering media is challenging for conventional imaging techniques.Remarkably,SWM retains its efficacy even in conditions of low signal-to-noise ratios.It facilitates the visualization of dynamic subcellular structures in live cells,encompassing tubular endoplasmic reticulum(ER),lipid droplets,mitochondria,and lysosomes.

Advancing nonlinear nanophotonics:harnessing membrane metasurfaces for third-harmonic generation and imaging

Dielectric metasurfaces are crucial for enhancing optical nonlinear generation,particularly membrane metasurfaces with multipolar resonances and compact size.Investigating silicon dimer-hole membrane metasurfaces,Rahmani,and Xu show how bound states in the continuum(BICs)can be formed and transformed into quasi-BICs by adjusting hole gaps.This innovation enables efficient conversion of infrared images to visible range,promising applications in nonlinear photonics and near-infrared imaging technologies.

Inversely engineered metasurfaces for independent manipulation of transmitted and reflected light fields

Independent manipulation of transmitted and reflected light fields is a key technology for the realization of multifunctional optical applications,which can be implemented based on multilayered plasmonic or supercell subwavelength structures.However,the former is not suitable for the optical bands,while the latter is insufficient in generating large phase gradients.Here,an adjoint-optimization-based inverse design methodology is proposed,which utilizes the polarization-selective local interference between individual meta-atoms and enables monolayer dielectric metasurfaces to decouple the wavefront of transmitted and reflected optical fields.Moreover,this methodology serves to mitigate the aperiodic electromagnetic crosstalk inherent between adjacent meta-atoms,consequently leading to a significant enhancement in the performance of meta-devices.We analyzed the physical mechanism of adjoint optimization and proposed the concept of phase factors,highlighting their importance in the rapid inverse design of meta-devices—an aspect often overlooked in previous research.To demonstrate the feasibility and robustness of our method,we optimize monolayer metasurfaces with different initial structures.These devices efficiently focus and deflect x-linearly and y-linearly polarized incident light in transmission and reflection spaces,respectively.Overall,this methodology holds immense potential for designing multifunctional,high-performing metasurfaces that meet multiple constraints,opening up broad prospects for applications.

一种用于大视场成像和偏振光谱探测的微型可重构超构光学系统

Wide-angle imaging and spectral detection play vital roles in tasks such as target tracking,object classification,and anti-camouflage.However,limited by their intrinsically different architectures,as determined by frequency dispersion requirements,their simultaneous implementation in a shared-aperture system is difficult.Here,we propose a novel concept to realize reconfigurable dual-mode detection based on electrical-control tunable metasurfaces.As a proof-of-concept demonstration,the simultaneous implementation of wide-angle imaging and polarization-spectral detection in a miniature sharedaperture meta-optical system is realized for the first time via the electrical control of cascaded catenary-like metasurfaces.The proposed system supports the imaging(spectral)resolution of approximately 27.8 line-pairs per millimeter(lp·mm^(-1);~80 nm)for an imaging(spectral)mode from 8 to 14 μm.This system also bears a large field of view of about 70°,enabling multi-target recognition in both modes.This work may promote the miniaturization of multifunctional optical systems,including spectrometers and polarization imagers,and illustrates the potential industrial applications of meta-optics in biomedicine,security,space exploration,and more.

Crosstalk-free achromatic full Stokes imaging polarimetry metasurface enabled by polarization-dependent phase optimization

Imaging polarimetry is one of the most widely used analytical technologies for object detection and analysis.To date,most metasurface-based polarimetry techniques are severely limited by narrow operating bandwidths and inevitable crosstalk,leading to detrimental effects on imaging quality and measurement accuracy.Here,we propose a crosstalkfree broadband achromatic full Stokes imaging polarimeter consisting of polarization-sensitive dielectric metalenses,implemented by the principle of polarization-dependent phase optimization.Compared with the single-polarization optimization method,the average crosstalk has been reduced over three times under incident light with arbitrary polarization ranging from 9μm to 12μm,which guarantees the measurement of the polarization state more precisely.The experimental results indicate that the designed polarization-sensitive metalenses can effectively eliminate the chromatic aberration with polarization selectivity and negligible crosstalk.The measured average relative errors are 7.08%,8.62%,7.15%,and 7.59%at 9.3,9.6,10.3,and 10.6μm,respectively.Simultaneously,the broadband full polarization imaging capability of the device is also verified.This work is expected to have potential applications in wavefront detection,remote sensing,light-field imaging,and so forth.

Simultaneously enhancing capacity and security in free-space optical chaotic communication utilizing orbital angular momentum

Optical chaotic signals emitted from an external-cavity feedback or injected laser diode enable small-signal information concealment in a noise-like carrier for secure optical communications.Due to the chaotic bandwidth limitation resulting from intrinsic relaxation oscillation frequency of lasers,multiplexing of optical chaotic signal,such as wavelength division multiplexing in fiber,is a typical candidate for high-capacity secure applications.However,to our best knowledge,the utilization of the spatial dimension of optical chaos for free-space secure communication has not yet been reported.Here,we experimentally demonstrate a free-space all-optical chaotic communication system that simultaneously enhances transmission capacity and security by orbital angular momentum(OAM)multiplexing.Optical chaotic signals with two different OAM modes totally carrying 20 Gbps on-off keying signals are secretly transmitted over a 2 m free-space link,where the channel crosstalk of OAM modes is less than-20 d B,with the mode spacing no less than 3.The receiver can extract valid information only when capturing approximately 92.5% of the OAM beam and correctly demodulating the corresponding mode.Bit error rate below the 7%hard-decision forward error correction threshold of 3.8×10^(-3)can be achieved for the intended recipient.Moreover,a simulated weak turbulence is introduced to comprehensively analyze the influence on the system performance,including channel crosstalk,chaotic synchronization,and transmission performance.Our work may inspire structured light application in optical chaos and pave a new way for developing future high-capacity free-space chaotic secure communication systems.

Towards the performance limit of catenary meta-optics via field-driven optimization

Catenary optics enables metasurfaces with higher efficiency and wider bandwidth,and is highly anticipated in the imaging system,super-resolution lithography,and broadband absorbers.However,the periodic boundary approximation without considering aperiodic electromagnetic crosstalk poses challenges for catenary optical devices to reach their performance limits.Here,perfect control of both local geometric and propagation phases is realized through field-driven optimization,in which the field distribution is calculated under real boundary conditions.Different from other optimization methods requiring a mass of iterations,the proposed design method requires less than ten iterations to get the efficiency close to the optimal value.Based on the library of shape-optimized catenary structures,centimeter-scale devices can be designed in ten seconds,with the performance improved by ~15%.Furthermore,this method has the ability to extend catenary-like continuous structures to arbitrary polarization,including both linear and elliptical polarizations,which is difficult to achieve with traditional design methods.It provides a way for the development of catenary optics and serves as a potent tool for constructing high-performance optical devices.

High-fidelity mode scaling via topologicaloptimized on-chip metalens for compact photonic interconnection

Photonic integrated circuits(PICs)have attracted significant interest in communication,computation,and biomedical applications.However,most rely on highly integrated PICs devices,which require a low-loss and high-integration guided wave path.Owing to the various dimensions of different integrated photonic devices,their interconnections typically require waveguide tapers.Although a waveguide taper can overcome the width mismatch of different devices,its inherent tapering width typically results in a long length,which fundamentally limits the efficient interconnection between devices with a high scaling ratio over a short distance.Herein,we proposed a highly integrated on-chip metalens that enables optical interconnections between devices with high width-scaling ratios by embedding a free-form metasurface in a silicon-on-insulator film.The special geometric features endow the designed metalens with high coupling efficiency and high integration.The device has a footprint of only 2.35μm in the longitudinal direction and numerical aperture of 2.03,enabling beam focusing and collimation of less than 10μm between devices with width-scaling ratio of 11.For the fundamental transverse electric field(TE0)mode,the relative transmittance is as high as 96%for forward incidence(from wide to narrow waveguides),whereas the metalens can realize wavefront shaping for backward incidence,which can be used in optical phase arrays.This study provides new ideas for optical interconnect design and wavefront shaping in high-integration PICs.Our design approach has potential applications in directional radiators,LiDAR,on-chip optical information processing,analogue computing,and imaging.

Classical and generalized geometric phase in electromagnetic metasurfaces

The geometric phase concept has profound implications in many branches of physics,from condensed matter physics to quantum systems.Although geometric phase has a long research history,novel theories,devices,and applications are constantly emerging with developments going down to the subwavelength scale.Specifically,as one of the main approaches to implement gradient phase modulation along a thin interface,geometric phase metasurfaces composed of spatially rotated subwavelength artificial structures have been utilized to construct various thin and planar meta-devices.In this paper,we first give a simple overview of the development of geometric phase in optics.Then,we focus on recent advances in continuously shaped geometric phase metasurfaces,geometric–dynamic composite phase metasurfaces,and nonlinear and high-order linear Pancharatnam–Berry phase metasurfaces.Finally,conclusions and outlooks for future developments are presented.