Gigahertz-rate-switchable wavefront shaping through integration of metasurfaces with photonic integrated circuit

Achieving spatiotemporal control of light at high speeds presents immense possibilities for various applications in communication,computation,metrology,and sensing.The integration of subwavelength metasurfaces and optical waveguides offers a promising approach to manipulate light across multiple degrees of freedom at high speed in compact photonic integrated circuit(PIC)devices.Here,we demonstrate a gigahertz-rate-switchable wavefront shaping by integrating metasurface,lithium niobate on insulator photonic waveguides,and electrodes within a PIC device.As proofs of concept,we showcase the generation of a focus beam with reconfigurable arbitrary polarizations,switchable focusing with lateral focal positions and focal length,orbital angular momentum light beams as well as Bessel beams.Our measurements indicate modulation speeds of up to the gigahertz rate.This integrated platform offers a versatile and efficient means of controlling the light field at high speed within a compact system,paving the way for potential applications in optical communication,computation,sensing,and imaging.

Neural network assisted high-spatial-resolution polarimetry with non-interleaved chiral metasurfaces

Polarimetry plays an indispensable role in modern optics.Nevertheless,the current strategies generally suffer from bulky system volume or spatial multiplexing scheme,resulting in limited performances when dealing with inhomogeneous polarizations.Here,we propose a non-interleaved,interferometric method to analyze the polarizations based on a tri-channel chiral metasurface.A deep convolutional neural network is also incorporated to enable fast,robust and accurate polarimetry.Spatially uniform and nonuniform polarizations are both measured through the metasurface experimentally.Distinction between two semblable glasses is also demonstrated.Our strategy features the merits of compactness and high spatial resolution,and would inspire more intriguing design for detecting and sensing.

Spin-decoupled meta-coupler empowered multiplexing and multifunction of guided wave radiation

Employing couplers to convert guided waves into free-space modes and flexibly control their wavefront is one of the key technologies in chip-integrated displays and communications.Traditional couplers are mainly composed of gratings,which have limitations in footprint,bandwidth,as well as controllability.Though the resonant/geometric metasurface newly emerges as a promising interface for bridging guided waves with free-space ones,it either relies on complex optimizations of multiple parameters,or is subject to the locked phase response of opposite spins,both of which hinder the functional diversity and practical multiplexing capability.Here,we propose and experimentally demonstrate an alternative with a spin-decoupled meta-coupler,simultaneously integrating triple functions of guided wave radiation,polarization demultiplexing,and dual-channel wavefront manipulation into a single device.By endowing polarization-dependent functionalities into a pure geometric metasurface,the out-coupled left-handed and right-handed circular polarization guided waves intelligently identify the predesigned phase modulation and reconstruct desired wavefronts,like bifocal focusing and holography multiplexing,with a polarization extinction ratio over 13.4 dB in experiments.We envision that the robust,broadband,and multifunctional meta-coupler could pave a way for the development of versatile multiplexed waveguide-based devices.

Metasurface empowered lithium niobate optical phased array with an enlarged field of view

Integrated optical phased arrays(OPAs) have attracted significant interest to steer laser beams for applications including free-space communications, holography, and light detection and ranging. Although many methods have been proposed to suppress grating lobes, OPAs have also been limited by the trade-off between field of view(FOV)and beamforming efficiency. Here, we propose a metasurface empowered port-selected OPA(POPA), an OPA steered by port selection, which is implemented by an aperiodic waveguide array with an average pitch less than the wavelength and phase controlled by coupling among waveguides. A metasurface layer above the POPA was designed to increase wide FOV steering, aliasing-free by polarization division. As a result, we experimentally demonstrate beam scanning over a ±41.04° × 7.06° FOV. The aliasing-free POPA with expanded FOV shows successful incorporation of the waveguide-based OPA technique with an emerging metasurface design, indicating much exploration in concepts for integrated photonic devices.