Open AccessPulse-width dependence of optical nonlinearities in As_2Se_3 chalcogenide glass in the picosecond-to-nanosecond region
Author(s) -
Kenta Shinkawa,
Kazuhiko Ogusu
Publication year - 2008
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.16.018230
Subject(s) - supercontinuum , materials science , optics , picosecond , ultrashort pulse , brillouin scattering , absorption (acoustics) , nanosecond , nonlinear optics , two photon absorption , attenuation coefficient , chalcogenide glass , pulse duration , chalcogenide , refractive index , laser , wavelength , optoelectronics , physics , photonic crystal fiber
We study the dependence of optical nonlinearities in As(2)Se(3) glass on the incident pulse-width using the Z-scan technique. In this work, 11.5-ns optical pulses from a Nd:YAG laser operating at 1.064 mum were compressed up to 1.6 ns by using stimulated Brillouin scattering in heavy fluorocarbon liquid, where the duration of the compressed pulses depends on the pump energy. Moreover picosecond optical pulses with a 1.053-mum wavelength were utilized for the Z-scan experiments. To investigate the pulse-width dependence of the optical nonlinearities leads to the separation of an ultrafast Kerr nonlinearity and a slow (cumulative) nonlinearity such as a thermal nonlinearity because the magnitude of the cumulative nonlinearity should be proportional to the pulse duration. The experimental results clearly show that both the nonlinear refractive index and the nonlinear absorption coefficient increase linearly with pulse width. The origin of such pulse-width dependence is presumably attributed to photostructural changes inherent in chalcogenide glasses, which are induced not by nonlinear absorption such as two-photon absorption or two-step absorption, but by linear absorption in the weak-absorption region.