Measurements of Cross-Correlations in a Two-Mode Dye Laser

Paul D. Lett

Lynn A. Westling, M. G. Raymer

The cross-correlation function between the pump and Stokes intensities in stimulated Raman scattering has been measured. It has previously been conjectured 1 and theoretically shown2 that the Stokes light generated in the presence of a multimode or broadband pump is generated with mode amplitudes and phases in perfect correlation with those of the pump. We present here experimental evidence of such cross correlations for scattering in hydrogen gas. The measurement technique used is the same as that previously used for measuring the intensity autocorrelation function of a multimode dye laser.3 This technique is based on detecting the frequency doubled light from a nonlinear crystal as a function of time delay between the pump and Stokes beams. We have performed cross-correlation measurements using as a pump the light from a multimode dye laser which is operated in two different cavity configurations: one in which the mode spacing Δυ is large compared with the spontaneous linewidth of the Raman transition Γ, Δυ > Γ; and one in which the mode spacing is small, Δυ < Γ.

Surendra Singh, L. Mandeļ

Maxi San Miguel, Luis Pesquera, Miguel A. Rodríguez +1 more

Exact formulas for the effective eigenvalue characterizing the initial decay of intensity correlation functions are given in terms of stationary moments of the intensity. Spontaneous emission noise and nonwhite pump noise are considered. Our results are discussed in connection with earlier calculations, simulations, and experimental results for single-mode dye lasers, two-mode inhomogeneously broadened lasers, and two-mode dye ring lasers. The effective eigenvalue is seen to depend sensitively on noise characteristics and symmetry properties of the system. In particular, the effective eigenvalue associated with cross correlations of two-mode lasers is seen to vanish in the absence of pump noise as a consequence of detailed balance. In the presence of pump noise, the vanishing of this eigenvalue requires equal pump parameters for the two modes and statistical independence of spontaneous emission noise acting on each mode.

Ronald F. Fox, Glenn E. James, Rajarshi Roy

A new, first-principles derivation of the equations for a quantized single-mode laser field pumped by a semiclassical stochastic field in a four-level molecular pumping scheme is presented. Computer simulations are used to generate fits to measured correlation functions for a single-mode dye laser.

Nageshwar Singh, H. S. Vora