Optical reflectivity of micromachined {111}-oriented silicon mirrors for optical input-output couplers

In this work, bulk-micromachined {111}-oriented silicon mirrors at 54.7 degrees have been fabricated in 20 wt% KOH solution at various temperatures and characterized with single-mode fibers (10/125 and 5/125). In fabricating the mirrors, the etch rate of the (100) silicon surface was widely varied from 5.3 to 73 mu m hr(-1) as the-processing temperatures were varied from 40 to 80 degrees C. In spite of the tremendous variation of etch rate, the measured reflectivities of the mirrors showed fairly stable values of 63.7-58% at 1330 nm and 55.4-57.7% at 1550 nm. This paper describes the silicon mirror processing conditions, measured reflectivities, reflected beam profiles, and a prototype integrated optical I-O coupler with the realized mirrors. The results obtained from this work show that optical I-O couplers with 54.7 degrees mirrors on conventional (100)-oriented silicon wafers are feasible, enabling us to envisage a synchronized optical clock distribution system as well as a distributed remote optical sensing system with low manufacturing cost.