Low-loss and broadband InP mirror-based out-of-plane optical coupler

Abstract

The authors developed a mirror-based out-of-plane optical coupler (MOOC) for InP photonic integrated circuits (PICs). The coupler has the coupling loss and alignment tolerance comparable to those of a conventional edge coupler. An asymmetric Mach–Zehnder interferometer (a-MZI) with the MOOC exhibits little wavelength-dependent loss (WDL) and a high extinction ratio (ER) of >20 dB over 100-nm wavelength bandwidth. In addition, the temperature-independent transmittance spectra were obtained. Finally, the authors fabricated a 4-ch MOOC array with the pitch of 40 μm, which corresponds to the core pitch of practical multi-core fibre (MCF).