Sensitive measurement of nonlinear refraction and two-photon absorption by spectrally resolved two-beam coupling

Abstract
A simple and very sensitive method for determining refractive and absorptive nonlinearities based on spectral resolution of two-beam coupling is demonstrated. Nonlinear phase shifts as small as 10-6 rad and two-photon absorption coefficients as small as 10-4 cm/GW are readily observed by use of this technique with nanojoule pulses from a mode-locked laser.