Sixth-order correlation on Raman-enhanced polarization beats with phase-conjugation geometry

Abstract

The correlation effects of sixth-order on the Raman-enhanced polarization beats (REPB) with phase-conjugation geometry in carbon disulfide are investigated using chaotic and phase-diffusion models. Based on two types of models, the cases that the pump beams have either narrow band or broadband linewidth are considered and it is found that the beat signal oscillates not only temporally with a 50.5 fs period but also spatially. The overall accuracy of using REPB to measure the resonant frequency of Raman-active vibrational mode is determined by the relaxation rates of the Raman mode and the molecular-reorientational grating. Moreover, the temporal behavior of the beat signal depends on the stochastic properties of the lasers and the decay rates of the Raman mode and the molecular-reorientational grating. Different stochastic models of the laser field only affect the sixth- and fourth-order coherence function. Furthermore, the different roles of the phase fluctuation and amplitude fluctuation have been pointed out in the time domain. The difference between the REPB and the fourth-order coherence on ultrafast modulation spectroscopy is discussed as well from a physical viewpoint. Therefore, the sixth-order coherence function theory of chaotic field is of vital importance in REPB.