title: Optical nonlinearities in hydrogenated-amorphous silicon waveguides.
abstract: We experimentally measure the optical nonlinearities in hydrogenated-amorphous silicon (a-Si:H) waveguides through the transmission of ultra-short pulses. The measured two-photon absorption coefficient beta is 4.1 cm/GW and we obtain a 3.5pi nonlinear phase shift at 4.1 W coupled input power corresponding to a nonlinear refractive index n(2) of 4.210(-13) cm(2)/W. The measured nonlinear coefficient gamma = 2003 (Wm)(-1) is at least 5 times the value in crystalline silicon. The measured free carrier absorption coefficient sigma = 1.910(-16) cm(2) agrees with the values predicted from the Drude-Lorenz model. It is seen that a-Si:H exhibits enhanced nonlinear properties at 1550 nm and is a promising platform for nonlinear silicon photonics.
authors.affiliation: Microsystems Engineering, Kate Gleason College of Engineering, Rochester Institute of Technology, Rochester, New York 14623, USA. kxn0404@rit.edu
authors.forename: Karthik
authors.initials: K
authors.lastname: Narayanan
authors.forename: Stefan F
authors.initials: SF
authors.lastname: Preble