Large-Optical-Aperture Top-Illuminated 50-Gbaud PIN-PD with High 3-dB Bandwidth at a Low Bias of 1.5 V. - Takashi Toyonaka; Hiroshi Hamada; Shigehisa Tanaka; Masatoshi Arasawa; Ryu Washino; Yasushi Sakuma; Kazuhiko Naoe (OFC, 2020)