High Power Indium Phosphide Photonic Integrated Circuit Platform

Abstract

High-power photonic integrated circuits (PICs) are of interest for a variety of applications including microwave photonics, free space optical communications and coherent LiDAR systems [1], [2]. Indium phosphide (InP) is the most advanced platform for high-performance PICs. InP PICs are particularly attractive for free space optical communications, which requires low cost, size, weight and power (CSWaP) [3]–[5]. In conventional InP PICs, saturation power of semiconductor optical amplifiers (SOAs) is limited by small modal size and high confinement factor ( $> 5\%$ ). To improve the SOA saturation power, one approach is to increase the modal size with a flared waveguide, but the large beam dimension in the horizontal direction imposes challenges on the coupling to singlemode fiber [6]. A second approach is to reduce the confinement factor. Slab-coupled optical waveguides (SCOW) with small confinement factor have been investigated for high-power SOAs and lasers. However, it is very challenging to monolithically integrate the SCOW SOAs with other optical elements required for a PIC such as a seed laser and modulator [7]. In this work, we have proposed a novel platform enabling the monolithic integration of low-confinement SOAs with other high-confinement components including a distributed Bragg reflector (DBR) laser and high-speed electro-absorption modulator (EAM).