Three-level nonlinear selective reflection at a glass–Cs-vapor interface

We present an experimental study of nonlinear selective reflection at a dielectric–Cs-vapor interface, in a three-level cascade-up scheme. The nonlinear reflection at the Cs ${\mathit{D}}_2$ resonance line is monitored in the presence of resonant irradiation at 621 nm or 658 nm (6${\mathit{P}}_{3/2}$→8${\mathit{D}}_{5/2}$,9${\mathit{S}}_{1/2}$). Experimental reflection spectra with either counterpropagating or copropagating light beams are analyzed and compared with the theoretical predictions of F. Schuller et al. [Phys. Rev. A 47, 519 (1993)]. For a blue-detuned pump and copropagating geometry an alternative type of three-level coherent reflection resonances, specifically associated with desorbing atoms, is observed. Also observed is the nonlinear reflection associated with the off-resonant, two-photon dispersion of atoms moving parallel to the window surface. Probe beam saturation is responsible for the appearance of additional resonant features in reflection spectra. Finally we analyze crossover spectral resonances which arise from nondegenerate, four-wave-mixing processes induced by the combined influence of counterpropagating pump and probe beams, and the pump beam being partially reflected by the window.