The refractive index of H<sub>2</sub> is shown to decrease linearly as a function of Stokes power and, to a much lesser extent, pump power in a nonresonant cw Raman laser. The dominant source of the index shift is shown to be thermal and significantly larger than dispersion associated with the Raman resonance. A steady-state theoretical model based on internal heating that is due to inelastic Raman scattering events accurately describes the observed behavior. With this model, frequency pulling of the Raman cavity resonance and phase distortions of the intracavity Gaussian beam are predicted for various levels of generated Stokes power.
© 2000 Optical Society of America
(140.3550) Lasers and laser optics : Lasers, Raman
(190.2640) Nonlinear optics : Stimulated scattering, modulation, etc.
(190.4870) Nonlinear optics : Photothermal effects
(190.5650) Nonlinear optics : Raman effect
(190.5890) Nonlinear optics : Scattering, stimulated
(190.5940) Nonlinear optics : Self-action effects
Peter A. Roos, Jay K. Brasseur, and John L. Carlsten, "Intensity-dependent refractive index in a nonresonant cw Raman laser that is due to thermal heating of the Raman-active gas," J. Opt. Soc. Am. B 17, 758-763 (2000)