EXPERIMENTAL-STUDY OF WAVE-GUIDE GRATING COUPLERS WITH PARALLELOGRAMIC TOOTH PROFILES

The fabrication process of waveguide grating couplers with parallelogr amic tooth profiles is described, using a novel reactive-ion etching ( RIE) geometry to generate oblique anisotropic etching. The blazing eff ect of nonresonant parallelogramic grating couplers is demonstrated ex perimentally, with nearly 90% radiation directionality measured. The r adiation factors of the grating couplers are also measured, and compar isons with simulated results show that the measured value is lower tha n that predicted theoretically. This is attributed to the deviation of the grating tooth profile from the ideal parallelogramic shape. (C) 1 996 Society of Photo-Optical Instrumentation Engineers.