Development of multi-step processing in silicon-on-insulator for optical waveguide applications

• Published in: Journal of optics. A, Pure and applied optics Pure and applied optics, 2006-07, Vol.8 (7), p.S455-S460
• Main Authors: Solehmainen, K, Aalto, T, Dekker, J, Kapulainen, M, Harjanne, M, Heimala, P
• Format: Article
• Language: English
• ISSN: 1464-4258
• DOI: 10.1088/1464-4258/8/7/S22

Multi-step processing for a silicon-on-insulator (SOI) platform was developed. It allows the incorporation of additional grooves and steps into the basic optical waveguide structures, so that light can be adiabatically coupled between waveguides with different cross-sections. The processes were based on simple fabrication methods easily scalable for mass production. Two options for the fabrication sequence were tested, both having one silicon etch step with an oxide mask and another etch step with a resist mask. The applicability of the developed processes was tested with different waveguide structures. An additional groove etched beside a bent 10 mum thick rib waveguide suppressed the bend losses to below 1 dB/90 deg with a 5 mm bending radius. A waveguide mirror exhibited optical losses below 1 dB/90 deg . The excess losses of a vertical taper between 10 and 4 mum thick rib waveguides were 0.7 dB. A converter between a rib and a strip waveguide showed negligible losses, below 0.07 dB.