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).