Quasi‐Static and Time‐Modulated Optical Phased Arrays: Beamforming Analysis and Comparative Study

Abstract

Herein, design procedures of the quasi‐static and time‐modulated optical phased arrays (OPAs) operating at near‐infrared spectrum are proposed and a comparative analysis over their dynamic beam‐steering functionalities is conducted. A metal–insulator–metal configuration integrated with indium tin oxide is considered as a building block of the reflective OPA. First, beamforming performance of the quasi‐static OPA, designed using the intuition‐based forward approach, is analytically studied and its main shortcomings posed by nonideal unit cell performance are highlighted. To surmount these limitations, an optimization‐based inverse design algorithm using multiobjective evolutionary optimization technique is proposed, which outputs non‐intuitive amplitude and phase profiles of the metal–insulator–metal supercells and identifies optimal beamforming tradeoffs between gain and sidelobe ratio of the quasi‐static OPA. Then, beam‐steering functionality of the time‐modulated OPA is investigated. Time‐modulated OPA affords 2π dispersionless phase shift, and constant amplitude at the sidebands, which lead to enhanced spectral and angular bandwidth, wide angle‐of‐view, and suppressed sidelobes. Following the fact that amplitude and phase of the sideband signals can be independently controlled through depth and phase delay of modulation, Taylor one‐parameter distribution is used to implement amplitude tapering for engineering the beamforming tradeoffs between gain and sidelobe levels of the time‐modulated OPAs.