High-quality-factor space–time metasurface for free-space power isolation at near-infrared regime  

作　　者：Raana Sabri Hossein Mosallaei 

机构地区：[1]Northeastern University,Department of Electrical and Computer Engineering,Boston,Massachusetts,United States

出　　处：《Advanced Photonics Nexus》2023年第6期83-95,共13页先进光子学通讯（英文）

基　　金：supported in part by Air Force Office of Scientific Research(Grant No.FA9550-18-1-0354).

摘　　要：Space–time metasurfaces are promising candidates for breaking Lorentz reciprocity,which constrains light propagation in numerous practical applications.There is a substantial difference between carrier and modulation frequencies in space–time photonic metasurfaces that leads to negligible spatial pathway variation of light and weak nonreciprocal response.To surmount this obstacle,herein,the design principle of a high-quality-factor space–time gradient metasurface is demonstrated at the near-infrared regime that increases the lifetime of photons and allows for strong power isolation by lifting the adiabaticity of modulation.The all-dielectric metasurface consists of an array of silicon subwavelength gratings(SWGs)that are separated from distributed Bragg reflectors by a silica buffer.The resonant mode with ultrahigh quality-factor exceeding 10^(4)is excited within the SWG,which is characterized as magnetic octupole and features strong field localization.The SWGs are configured as multijunction p–n layers,whose multigate biasing with time-varying waveforms enables modulation of carriers in space and time.The proposed nonreciprocal metasurface is exploited for free-space optical power isolation by virtue of modulationinduced phase shift.It is shown that under time reversal and by interchanging the directions of incident and observation ports,power isolation of≈35 dB can be maintained between the two ports in free space.

关 键 词：space-time metasurface high-Q resonator optical nonreciprocity active photonic platform. 

分 类 号：O43[机械工程—光学工程]