<title>Reflectivity of micromachined {111}-oriented silicon mirrors for optical input/output couplers</title>

Abstract

In this work, bulk-micromachined { 1 1 1}-oriented silicon mirrors at 54.7° have been fabricated in 20 wt% KOH solution at various temperatures and characterized with single mode fibers (10/125 and 51125). In fabricating the mirrors, the etch rate of the (100) silicon surface was widely changed from 5.3 tm/hr to 73 jim/hr as the processing temperatures were varied from 40 °C to 80 °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 respectively. 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° mirrors on conventional (100)-oriented silicon wafers are feasible, envisaging a synchronized optical clock distribution system as well as a distributed remote optical sensing system with low manufacturing cost.

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

“…A major component of the OEMCM, and the focus of this paper, is the micromachined silicon mirror or optical I-O coupler which can be fabricated using standard silicon micromachining techniques such as wet anisotropic etching in KOH [3][4][5][6]. The micromachined mirror should have the capability of reflecting the input optical beam to a photodetector positioned vertically from the incident direction, thus allowing for the realization of an integrated optical I-O coupler [7]. In addition to their importance in OEMCMs, optical I-O couplers will also find applications in optical communications and signal processing.…”

“…Standard anisotropic etching techniques can be used to expose {111} planes since they etch so much more slowly than any other crystal plane in etchants such as KOH. For this reason, {111} planes have been widely investigated as reflecting surfaces [7][8][9][10]. Although a 45 • mirror would seem the logical choice for an optical I-O coupler, a nonstandard wafer whose polished surface is 9.7 • out of the (100) plane is required as the substrate if one wishes to use {111} planes as the 45 • reflecting surfaces.…”