| In this work nonlinear refractive index changes associated with avalanche absorption of Tm:LiYF;Nearly-degenerate two-beam coupling techniques were employed for the bulk of the experimental measurements reported here. Real and imaginary parts of the nonlinear refractive index, as well as response times of the nonlinearities, were determined versus light intensity and wavelength. High resolution spectroscopic studies provided a modified picture of the basic mechanism of avalanche upconversion dynamics. Enhancement of the avalanche nonlinearity in a resonant cavity resulted in self-pulsing of the upconversion emission and cavity transmission. Self-locking of a cavity to the laser frequency without external electronics was also observed, due to avalanche-mediated thermal nonlinearities in the system. |
