Development of a vertical optical coupler using a slanted etching of InP/InGaAsP waveguide. - Sunghan Choi; Akio Higo; Masaru Zaitsu; Myung-Joon Kwack; Masakazu Sugiyama; Hiroshi Toshiyoshi; Yoshiaki Nakano (IEICE Electron. Express, 2013)