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.

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.

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.

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.