Abstract

A new optical interconnect technique is demonstrated for optical communication to a VLSI chip which is suitable for very high packing densities. This interconnect features small size (<10 µm), reproducible and accurate alignment between the optical fiber and the electronic device, and mechanically stable, high efficiency coupling. The basic idea (for a receiver structure) is to etch a hole slightly larger than a single-mode fiber core into a silicon wafer by a laser-assisted etching technique. A p-n junction is then formed on the inside of the hole and serves as a detector. As a result of the hole geometry, the fabrication process of the p-n junction requires a modification of the conventional technique used in the surface diffusion of a p-n junction. In the final stage, an optical fiber is uniformly stretched and is inserted into the hole and is affixed by means of epoxy. Here the objective is to reduce a single-mode fiber to the dimensions necessary for insertion into the hole, while preserving its guiding properties. With the fiber secured in the hole, light emanating from the end of the fiber is collected by the reverse biased junction and converted to an electrical signal. This signal can be utilized by circuitry on the surface of the wafer. In this way, the footprint of the integrated fiber-optic coupler on the chip is nearly equal to the cross-sectional area of the single-mode optical fiber core, and arrays of such interconnects can achieve very high packing densities.

© 1985 Optical Society of America