Collisional broadening of nonlinear optical resonances

Sergei I Yakovlenko

G. Grynberg

Bruce J. Herman, Joseph H. Eberly, Michael G. Raymer

We undertake a theoretical investigation of the coherent optical propagation of Stokes light in a collisionally broadened three-level Raman amplifier. The Stokes light consists of two distinct spectral components: off-resonance stimulated Raman scattering and on-resonance stimulated fluorescence, induced by collisional transfer of population to a near-resonant intermediate state of the atomic system. Our model is based on the semiclassical Maxwell-Bloch formalism where the separation of the Stokes light into two components results in an expansion from the usual 9 to 13 atomic variables. We investigate the model both analytically and numerically. We point out the physical contributions to the simultaneous evolution of pump, fluorescence, and Raman light. We discuss the development during propagation of these separate pulses, emphasizing the nonlinear effects that lead to saturation.

A. Szöke

The collisionally broadened optical absorption cross section that is constant at low intensities is predicted to decrease at high intensities. The prediction is based on a nonlinear change of the effective interaction of the atom with the strong incident electromagnetic field and a distortion of the atomic interaction potential by it. An experiment is analyzed here that observes this falloff on the “wing” of the 460.73-nm strontium resonance line, collision broadened by an argon buffer gas. Qualitative agreement is reached between theory and experiment when the degeneracy of the levels is taken into account.

F. W. Byron

Sergei I Yakovlenko

This review gives a systematic exposition of the qualitative problems of nonlinear laser resonance spectroscopy, taking into account the effect of the light field on the dynamics of the broadening collision and, correspondingly, on the rate of phase relaxation. The results of experiments, in which these nonlinear optocollisional effects, predicted earlier theoretically, were observed, are presented briefly.