Wide-bandwidth, low-waveguide-width-sensitivity InP-based multimode interference coupler designed by wavefront matching method. - Takeshi Fujisawa; Tsutomu Kitoh; Kei Watanabe; Kenya Suzuki; Masaki Kotoku; Hiroshi Takahashi (IEICE Electron. Express, 2011)

Ultra-compact Reflow-compatible Detachable Optical Connector for Co-Packaged Optics. - Kengo Watanabe; Shosuke Ikeda; Yuki Fujimaki; Tsunetoshi Saito; Masaki Kotoku (OFC, 2025)