Nonlinear resonant polarization rotation under conditions of coherent population trapping

Nonlinear resonant optical rotation was studied over a wide range of experimental parameters at the Rb $D_1 F=2\to F'=1$ transition in the $^{87}$Rb vapor under conditions of coherent population trapping. The angle of rotation was found to depend nonmonotonically on the laser intensity and applied magnetic field. The effect of optical pumping out to the level $F=1$ is discussed. It is demonstrated experimentally that the Faraday rotation angle increases twofold upon the compensation for pumping.