Amorphous silicon waveguides for microphotonics

• Published in: Journal of applied physics 2002-07, Vol.92 (2), p.649-653
• Main Authors: de Dood, M. J. A., Polman, A., Zijlstra, T., van der Drift, E. W. J. M.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1486055

Amorphous silicon a-Si was made by ion irradiation of crystalline silicon with 1×1015 Xe ions cm−2 at 77 K in the 1–4 MeV energy range. Thermal relaxation of the amorphous network at 500 °C for 1 h leads to an amorphous layer with a refractive index of n=3.73, significantly higher than that of crystalline silicon (n=3.45 at λ=1.55 μm). a-Si can thus serve as a waveguide core in Si based optical waveguides. Channel waveguides were made by anisotropic etching of a 1.5 μm silicon-on-insulator structure that was partly amorphized. Transmission measurements of these waveguides as function of the amorphous silicon length show that the a-Si part of the waveguides exhibit a modal propagation loss of 70 cm−1 (0.03 dB μm−1) and a bulk propagation loss of 115 cm−1 (0.05 dB μm−1). Losses due to sidewall roughness are estimated, and are negligible compared to the modal loss.