We present a technique to lithographically define and fabricate all required optical facets on a silicon-on-insulator photonic integrated circuit by an inductively coupled plasma etch process. This technique offers 1 μm positioning accuracy of the facets at any location within the chip and eliminates the need of polishing. Facet fabrication consists of two separate steps to ensure sidewall verticality and minimize attack on the end surfaces of the waveguides. Protection of the waveguides by a thermally evaporated aluminum layer before the 40-70 μm deep optical facet etching has been proven essential in assuring the facet smoothness and integrity. Both scanning electron microscopy analysis and optical measurement results show that the quality of the facets prepared by this technique is comparable to the conventional facets prepared by polishing.

Journal of Vacuum Science and Technology A
Department of Electronics

Yap, K.P., Lamontagne, B., Delâge, A., Janz, S., Bogdanov, A., Picard, M., … Syrett, B. (2006). Fabrication of lithographically defined optical coupling facets for silicon-on-insulator waveguides by inductively coupled plasma etching. Journal of Vacuum Science and Technology A, 24(3), 812–816. doi:10.1116/1.2186657