Broadband All-Optical Modulation in Hydrogenated-Amorphous Silicon Waveguides

the authors demonstrate broadband all-optical modulation in low loss hydrogenated-amorphous silicon (a-Si:H) waveguides. Significant modulation (~3 dB) occurs with a device of only 15 £gm without the need for cavity interference effects in stark contrast to an identical crystalline silicon waveguide. the authors attribute the enhanced modulation to the significantly larger free-carrier absorption effect of a-Si:H, estimated here to be ?O?P = 1.63?Q10?O16?Q?ON cm?O1. In addition, the authors measured the modulation time to be only ?Rc ~400 ps, which is comparable to the recombination rate measured in sub-micron crystalline silicon waveguides, illustrating the strong dominance of surface recombination in similar sized (460 nm x 250 nm) a-Si:H waveguides.