InP-Based Butt-Joint Coupled Waveguide Photodiodes Integrated With Various Functions for 100 GBaud Coherent Detection
Takuya Okimoto, Hideki Yagi, Koji Ebihara, Kouichiro Yamazaki, Satoru Okamoto, Yusuke Ohkura, Kazuhiko Horino, Munetaka Kurokawa, Masaru Takechi, Mitsuru Ekawa, Yoshihiro Yoneda
Abstract
This paper reports on the performance of an InP-based butt-joint (BJ) coupled waveguide photodiode (PD) for 100 GBaud coherent detection. We adopt a dual-layer absorber comprised of p- and i-type GaInAs absorption layers to enhance the advantage of BJ coupled waveguide PDs which overcome the tradeoff between high responsivity and wide bandwidth. As a result, a responsivity as high as 0.90 A/W over the C-band and a wide 3 dB bandwidth of 71 GHz have been successfully obtained at a reverse bias voltage of 2.5 V. Towards the realization of compact coherent modules without complicated assembly processes, we have also fabricated a compact photonic integrated circuit (PIC) chip (Chip size: 2.6 × 4.1 mm) configured by 12 BJ coupled waveguide PDs and various optical functions, such as 90° hybrids and variable optical attenuators (VOAs) through the InP-based monolithic integration technology. An integrated coherent transmitter-receiver optical sub-assembly (IC-TROSA) employing the PIC has exhibited receiver performance sufficient for 100 GBaud coherent detection.