Saturated absorption spectroscopy with limited crossovers by use of copropagating beams configuration

Abstract

The crossovers in conventional saturated absorption spectroscopy (SAS) are always harmful and undesired, especially for those pairs of transitions with very small frequency differences. To reduce the number and intensity of the crossovers, two copropagating beams from one laser were employed to detect SAS of rubidium (Rb) D2 line at 780 nm. It is found that only one weak crossover exists among the three atomic natural resonances in copropagating-SAS instead of three strong ones in the conventional SAS. Besides, the position of the crossover can be modulated by adjusting the angle between the two copropagating beams. The atomic natural resonances were explicitly identified as the crossover is displaced. This method helps to identify the atomic natural resonances in SAS and prevent the crossovers from interfering in the atomic natural resonances, which is meaningful in the applications of SAS.