Abstract

For optical computing and optical interconnection of electronic integrated circuits it is desirable to have 2-D arrays of interconnects. By doing so one gains the tremendous advantage of optical interconnects to utilize the entire area of the chip rather than just the perimeter. For such systems free-space optics has been the primary transmission medium considered. Optical fibers are possibly a more convenient medium, but the mechanical difficulties of fabricating a 2-D array of fibers are formidable. We present a new type of optical component, a monolithic optical fiber stub array (MOFSA). It is formed out of Corning Fotoform glass, which has the property that, when exposed to ultraviolet light and thermally cycled, it becomes highly soluble in hydrofluoric (HF) acid. Thus features can be formed in the glass via photolithographic techniques. Additionally, since only exposed regions are etched, extremely high aspect ratios can be achieved. Our MOFSA is formed by masking a 1.5-mm thick Fotoform glass plate with 65-μm diameter circular dark fields on 400-μm spaced centers and exposing and heating. The sample is then placed in an agitated HF solution. The etching proceeds from both faces, and is timed to stop when there is still a 250-μm thick central plane, producing 600-μm long fibers extending from either face. The fibers are ~65-μm diameter at the base and 55-μm diameter at the tip. The fiber tips are subsequently mechanically polished (wax is first melted, flowed between the fibers and cooled to form a support). After removing the wax, we focused a 632.8-nm He-Ne laser (with an ~1-mm diameter beam) onto a fiber tip with a 10× objective and achieved 56% transmission (-2.5-dB insertion loss).

© 1991 Optical Society of America