An abnormal phenomenon in the saturated absorption spectrum of ⁸⁷Rb

A polarization-type saturated absorption spectrum set-up for ^87Rb atom laser cooling and trapping has been established in our laboratory. By changing the polarization components and optical power, enhanced absorption of the transition 5S_1/2 F=2→5P_3/2F^′=3 was observed with other transitions and cross-over resonance staying unvaried.