Design of GaSb-based monolithic passive photonic devices at wavelengths above 2 µm

Abstract

In this paper, we report, for the first time, a theoretical study on passive photonic devices including optical power splitters/combiners and grating couplers operating at non-telecom mid-wave infrared wavelengths. Passive components were designed to operate, in particular, at around 2.6 µm for monolithic integration with active photonic devices on the III-V gallium antimonide material platform. The three popular types of splitters/combiners such as directional couplers, multimode interferometer-, and Y-branch-couplers were theoretically investigated. Based on our optimized design and rigorous analysis, fabrication-compatible 1×2 optical power splitters with less than 0.12 dB excess losses, large spectral bandwidth and a 50:50 splitting ratio are achieved. For fiber-to-chip coupling, we also report the design of grating couplers with an outcoupling efficiency of ~29% at 2.56 μm and 3-dB bandwidth of 80 nm. The results represent a significant step towards developing a complete functional photonic integrated circuits at mid-wave infrared wavelengths.