We report an extension of the spectrally resolved two-beam coupling technique to measure the nonlinear intensity index of refraction (n<sub>2</sub><sup>I</sup>) and the two-photon absorption coefficient (β) by use of chirped laser pulses. The linear chirp parameter <i>b</i> is incorporated into the derivation of a more general model than the previous one [Opt. Lett. <b>22</b>, 1077 (1997)]. We have also analyzed the validity of this linear chirp model through a comparison of the experimental results for fused silica with the numerically accurate calculation that considers higher-order chirps obtained by second-harmonic generation frequency-resolved optical gating. The results show that this method potentially can be used to extract the chirp. Finally, we applied this transient spectrally resolved nonlinear transmittance spectroscopy to semiconductor-doped glasses to extract their n<sub>2</sub><sup>I</sup> and β.
© 1999 Optical Society of America
(190.7110) Nonlinear optics : Ultrafast nonlinear optics
(320.1590) Ultrafast optics : Chirping
(320.7100) Ultrafast optics : Ultrafast measurements
(320.7110) Ultrafast optics : Ultrafast nonlinear optics
J.-K. Wang, T.-L. Chiu, C.-H. Chi, and C.-K. Sun, "Nonlinear refraction and absorption measurements with chirped femtosecond laser pulses: experiments and simulations," J. Opt. Soc. Am. B 16, 651-661 (1999)