Nonlinear refraction and absorption measurements with chirped femtosecond laser pulses: experiments and simulations

We report an extension of the spectrally resolved two-beam coupling techniq ue to measure the nonlinear intensity index of refraction (n(2)(I)) and the two-photon absorption coefficient (beta) by use of chirped laser pulses. T he linear chirp parameter b is incorporated into the derivation of a more g eneral, model than the previous one [Opt. Lett. 22, 1077 (1997)]. We have a lso analyzed the validity of this linear chirp model through a comparison o f the experimental results for fused silica with the numerically accurate c alculation that considers higher-order chirps obtained by second-harmonic g eneration frequency-resolved optical gating. The results show that this met hod potentially can be used to extract the chirp. Finally, we applied this transient spectrally resolved nonlinear transmittance spectroscopy to semic onductor-doped glasses to extract their n(2)(I) and beta. (C) 1999 Optical Society of America [S0740-3224(99)00804-8] OCIS codes: 190.7110, 320.7100, 320.7110, 320.1590.