Influence of radiation intensity on resonant Faraday rotation in potassium vapor

The Faraday effect in potassium vapor pumped by nanosecond pulses of near resonant laser radiation is studied experimentally. The input radiation with linewidth 3 cm-1 had a central frequency vp equals 13055 cm-1 which was 12 cm-1 higher than 4S1/2 - 4P3/2 atomic transition frequency v0 equals 13043 cm-1. The strong spectral broadening of pump radiation allowed to observe the Faraday rotation at frequencies v+/- 1 equals v0 +/- 2.5 cm-1 located closer to the atomic resonance where the rotation was high. The decrease of Faraday rotation from 150 degree(s) to 20 degree(s) with the increase of the intensity of pump radiation from 2 (DOT) 105 to 107 W/cm2 has been measured. The saturation of 4S1/2 - 4P3/2 transition is considered as a cause of suppression of Faraday rotation. The contributions of one photon resonance absorption, as well as of multiphoton processes, caused by more intense off resonant part of the broadened pump radiation (having frequency detuning 12 cm-1), to saturation of resonant transition is discussed. The experimental results are compared with theoretical calculations performed.