Abstract

Waveguide photodetectors have received a great deal of interest recently because they overcome the bandwidth-efficiency trade-off in conventional surface-illuminating p-i-n photodetectors [ 1][2]. Bandwidth-efficiency products exceeding 100 GHz have been predicted for these devices. The main disadvantage of waveguide-type photodetectors is the low optical coupling efficiency from optical fibers. Thus the increase of the internal quantum efficiency was often offset by the low coupling efficiency. A multimode waveguide structure has been proposed to improve the input coupling efficiency from 40% to 68%, while maintaining a bandwidth of 50 GHz [2]. However, the absorption efficiency of high-order modes is low because of mode mis-match. In addition, the coupling efficiency becomes very sensitive to misalignment.

© 1994 Optical Society of America