Amorphous silicon-based guided-wave passive and active devices for siliconintegrated optoelectronics

Waveguides and interferometric light amplitude modulators for application a t the 1,3- and 1.55-mu m fiber communication wavelengths have been fabricat ed with thin-film hydrogenated amorphous silicon and its related alloys, Th e technique adopted for the thin-film growth is the plasma-enhanced chemica l vapor deposition, which has been shown to give the lowest defect concentr ation in the film. Consequently the proposed waveguiding structures take ad vantage of the low optical absorption shown by a-Si:H at photon energies be low the energy gap. In addition a good radiation confinement can be obtaine d thanks to the bandgap tailoring opportunity offered by this simple and in expensive technology, In particular rib waveguides, based on a a-SiC:Wa-Si:H stack, have been rea lized on crystal silicon, showing propagation losses as low as 0.7 dB/cm, T he same structure has been utilized for the fabrication of thermooptic Fabr y-Perot modulators with switching times of 10 mu s. Modulators based on the alternative waveguiding configuration ZnO/a-Si:H, giving comparable result s, are also presented.