Coherent population trapping resonances in the presence of the frequency-phase noises of an exciting field

The influence of noises of the frequency and phase difference of an exciting bichromatic field on the parameters of coherent population trapping resonances is studied experimentally. When the phase difference fluctuates within a limited interval near its average value with a short correlation time, the resonance contrast decreases proportionally to exp(-φ²_rms), where φ²_rms — is the phase dispersion (in rad²). In this case, the spectral width of the resonance remains constant. In another limiting case, when the phase noise has a long correlation time, the resonance contour broadens, the area under the contour being invariable. Experiments were performed with the Zeeman sublevels of the ground state of ⁸⁷Rb by exciting rubidium vapour in a glass cell at the resonance wavelength of 795 nm.