Higher-order correlation on polarization beats in Markovian stochastic fields

The correlation effects of sixth order on cascade three-level polarization beats are investigated using chaotic field, phase-diffusion, and Gaussian-amplitude models. The polarization beat signal is shown to be particularly sensitive to the statistical properties of the Markovian stochastic light fields with arbitrary bandwidth. Different stochastic models of the laser field only affect the sixth- and fourth-order coherence functions. The constant background of the beat signal originates from the amplitude fluctuation of the Markovian stochastic fields. The Gaussian-amplitude field shows fluctuations larger than the chaotic field, which again exhibits fluctuations much larger than for the phase-diffusion field with pure phase fluctuations caused by spontaneous emission. The cases that the pump beams have either narrowband or broadband linewidth are considered and it has been found that for both cases a Doppler-free precision in the measurement of the energy-level difference of the excited states can be achieved. The sixth-order coherence function theory is of vital importance in cascade three-level polarization beats.