We report experimental and theoretical results of two symmetrical signals of degenerate four-wave mixing generated in rubidium vapor. Both nonlinear signals are induced by two almost copropagating laser beams, with and wave-vectors, and detected simultaneously in the and directions. In each direction, we observe a single peak when the two beams are tuned on the closed transition ⁸⁵Rb 5S _1/2(F = 3) → 5P _3/2(F = 4). The excitation spectra reveal a small frequency separation between the two peaks, which is explained when propagation effects are taken into account. Furthermore, our theoretical analysis shows that a correct description of the frequency position of each peak is achieved with a variable refractive index for both lasers, in which the scanning laser experiences an anomalous window in the refractive index near resonance.

我们报告experimental蒸汽中生成的简并四波混合的两个对称信号的实验和理论结果。这两个非线性信号都是由两个几乎同时传播的激光束（和）和波矢量（）感生的，并且在和方向上同时被检测到。在两个方向上的两个光束在闭合过渡处调谐时，我们在每个方向上观察到一个峰值⁸⁵ Rb 5 S _1/2（F = 3）→5 P _3/2（F= 4）。激发光谱显示出两个峰之间的频率间隔很小，这在考虑传播效应时得到了解释。此外，我们的理论分析表明，对于两个激光器，都可以通过可变的折射率来正确描述每个峰的频率位置，其中扫描激光器在谐振附近的折射率处出现异常窗口。