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The absorption spectra of Nd3+ in pure anhydrous neodymium chloride crystals and in anhydrous praseodymium chloride crystals (containing 0.1% NdCl3) have been examined systematically examined. The structures of the groups of their absorption lines are found to be similar to those of Nd3+ in NdCl3 crystals diluted by LaCl3 (containing 2% NaCl3 in LaCl3), except for a shift of the spectrum towards the long wave side. The shifts (relative to the ground state) of these corresponding sub-levels are proportional to the length of unit cell of the single crystals.

High resolution polarized absorption spectra in visible and ultra-violet spectral region have been examined sysmatically. We have mainly determined the stark sublevels and their irreducible representations for the higher energy levels. We find that the groups of their absorption lines are corresponding to those of Br3+ in CaWOLiYF4 and in LaFLiYF3, but there exist sysmatically shifts between the centers of gravity of energy levels in these three different crystals.

The reflection behavious of nonlinear optical interface between glass and liquid crystal were studied systematically. The reflection behaviours of such interface with isotropic liquid phase was studied by using a Q-switched ruby laser. The threshold intensity of transition from TIR (tolal internal reflection) to partial transmission for different incident angle were measured at T-Tc = 2.5℃. It agrees with the plane wave theory of Kaplan. The time resolved reflection of nonlinear interface was also measured and hysteresis loop of reflectivity was observed. The hysteresis loop of reflectivity can be attributed to the deorientation relaxation processes of liquid crystal molecules. The nonlinear optical interface between glass and ne-matic liquid crystal was also studied using an Ar+ laser. The transition from TIR to partial transmission was observed at the intensity 700 W/cm2. This transition can be attributed to thermal induced phase transition from nematic mesophase to isotropic liquid phase.