Abstract

Waveguide coupling to absorbing layers is essential for photodetector integration in OEICs. Evanescent coupling schemes (Fig. 1) are the simplest to fabricate, but exhibit weak coupling. Long devices are required for appreciable absorption, resulting in large capacitance and small bandwidth.^1-3 Improved coupling is achievable by using thin waveguide layers^1,2 or thin absorbers,^2,3 but these designs result in difficult fiber-to-waveguide coupling or excessive photodiode capacitance, respectively. Here we present a novel method that improves evanescent coupling ≥7× over conventional structures, preserves simplicity of fabrication, and applies to all guide and absorber thickness values.

© 1990 Optical Society of America