Amorphous silicon waveguides and interferometers for low-cost silicon optoelectronics

The present work reports on our recent achievements in the exploitation of a simple technology for the fabrication of hydrogenated amorphous silicon (a-Si:H) based low-loss rib waveguides. In particular, waveguides with various widths have been fabricated out of an a-SiC:H/a-Si:H stack deposited by plasma enhanced chemical vapor deposition at the relatively low temperature of 220 degrees C. The ribs were defined by an anisotropic, CH4-based, reactive ion etching process. The devices have been subsequently characterized by cut-back technique. Even though a dependence of attenuation parameter on the waveguide width was observed, propagation losses as low as 0.7 dB/cm could be measured at λ=1.3 μm, in good agreement with he theoretical estimations based on the intrinsic absorption of the material. Starting from the same structure, a Fabry- Perot thermo optical modulator has been also fabricated and tested at the communication wavelength of 1.3 μm.