title: Ultrafast nonlinear effects in hydrogenated amorphous silicon wire waveguide.
abstract: We, for the first time, present the ultrafast optical nonlinear response of a hydrogenated amorphous silicon (a-Si:H) wire waveguide using femtosecond pulses. We show cross-phase and cross-absorption modulations measured using the heterodyne pump-probe method and estimate the optical Kerr coefficient and two-photon absorption coefficient for the amorphous silicon waveguide. The pumping energy of 0.8 eV is slightly lower than that required to achieve two-photon excitation at the band gap of a-Si:H (approximately 1.7 eV). An ultrafast response of less than 100 fs is observed, which indicates that the free-carrier effect is suppressed by the localized states in the band gap.
authors.affiliation: Network Photonics Research Center, National Institute of Advanced Industrial Science and Technology, 1-1-1Umezono, Tsukuba, Ibaraki 305-8568, Japan. y-shoji@aist.go.jp
authors.forename: Yuya
authors.initials: Y
authors.lastname: Shoji
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ogasawara
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Kamei
authors.forename: Youichi
authors.initials: Y
authors.lastname: Sakakibara
authors.forename: Satoshi
authors.initials: S
authors.lastname: Suda
authors.forename: Kenji
authors.initials: K
authors.lastname: Kintaka
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kawashima
authors.forename: Makoto
authors.initials: M
authors.lastname: Okano
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Hasama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishikawa
authors.forename: Masahiko
authors.initials: M
authors.lastname: Mori
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D006859:Hydrogen / Q000737:chemistry*; D017711:Nonlinear Dynamics; D012031:Refractometry / Q000295:instrumentation*; D012825:Silicon / Q000737:chemistry*
chemical_list: D006859:Hydrogen; D012825:Silicon