Abstract

10-ns (FWHM) Gaussian-shaped pulses at 1.064 pm from an injection seeded Nd:YAG laser have been shown to be modulated temporally after passing through a 1-mm etalon made of the semiconductor material CdTe. The etalon, having a finesse of <2, exhibits linear transmission of the laser until a laser fluence level of ≥100 mj/cm² is reached. As the fluence level increases beyond the threshold, the etalon transmission starts to decrease together with compression of the laser pulse up to a factor of 2, as a result of the detuning of the etalon resonance from the laser frequency. A further fluence increase results in periodic modulations of the incident Gaussian profile showing both maxima and minim superimposed on a fast quasiexponential decay. The periodic modulations can be explained as due to the successive tune in and out of the etalon resonances. A possible mechanism responsible for the nonlinear etalon effect might be two-photon absorption through intermediate states. This process creates free carriers of electron–hole pairs that change the index of refraction of the etalon. Modeling of these pulses modulations must take into account the generation, as well as diffusion and recombination, of these free carriers. The modeling is in progress.

© 1991 Optical Society of America