This dissertation is concerned with optical phase conjugate waves generated in cryptocyanine and ruby crystal.
The phase conjugate(PC) mirror system consisting of a and amplifier and a nonlinear medium is presented and the theoretical analysis of enhanced PC wave in the system is derived by taking into account of the overlap of the probe and counterpropagating PC wave in the amplifier. In order to examine experimentally the enhanced PC reflectivity in degenerate four wave mixing (DFWM) an amplifier is placed in the probe beam path. A Q-switched ruby laser is a light source, and a ruby rod of 6mm (diameter)×76mm (length) and cryptocyanine dissolved methanol are used for the amplifier and the nonlinear medium, respectively. Experimental result of maximal $R_{enh}/R$=3.9±0.25 is obtained where R and $R_{enh}$ are PC reflectivities in the absence and presence of the amplifier, respectively. The experimental results agree within 5% with the theoretical values.
Next, the anisotropic properties of PC wave generated in a ruby crystal are investigated.
The real part $n'_2$ of the complex nonlinear refractive index coefficients of ruby crystal $(Cr^{3+}:Al_2O_3)$ induced by $Ar^+$ ion laser (5145$\mathring{A}$), are measured by Mach-Zehender interferometric method. The $n'_2$ measured at same pumping beam wavelength for the light polarization perpendicular ($\sigma$) and parallel ($\pi$) to the crystal c-axis are (2.81±0.36)×$10^{-8} cm^2/W$ and (1.33±0.17)×$10^{-8} cm^2/W$, respectively. The measured values are useful for the DFWM experiments in ruby crystal.
The isotropic DFWM theory can not be applied in the uniaxial crystal as ruby, since both of the ordinary (o) and extraordinary (e) gratings are formed by the o-waves and e-waves, respectively. An anisotropic DFWM theory is derived considering both the transmission and reflection gratings by the treatment of the o-waves and e-waves separately. The experiments are performed for two cases. In one the o-grating vector equals to e-grating vector, so that the o-and e-gratings have the same Bragg diffraction conditions but in the other otherwise. The experimental results agree within 5% with the theoretical values calculated by using the $n'_{2A\sigma}$ and $n'_{2A\pi}$ measured before.
