Physical Review A
Light scattering and nonlinear optical response near a critical point
Robert M. McGraw
Abstract
The connection between light scattering and nonlinear optical response is examined quantitatively for Kerr media and is generalized to include isotropic materials with nonlocal interactions near a critical point. A number of important quantities, including the nonlinear refractive index (${\mathit{n}}_{2}$) and the four-wave-mixing coefficient, are shown to acquire increasing grating wave-vector (q) dependence as the critical point is approached. This dependence is identical to the q dependence obtained for light scattering in the Ornstein-Zernike theory. Illustrative calculations are presented for near-critical xenon using the Redlich-Kwong equation of state and parameters obtained from independent measurements. These results indicate ${\mathit{n}}_{2}$ values of ${10}^{\mathrm{\ensuremath{-}}15}$--${10}^{\mathrm{\ensuremath{-}}14}$ ${\mathrm{m}}^{2}$/W and response times in the 1--10-\ensuremath{\mu}sec range. Calculations are presented for the phase-conjugate reflectivity in degenerate four-wave mixing that include both nonsaturable background loss and light-scattering noise. Reflectivities in excess of unity are predicted for 1.06-\ensuremath{\mu}m wavelength and cw pump intensities in the 10-kW/${\mathrm{cm}}^{2}$ range.