Experimental and numerical evaluation of pump energy absorption in a side-pumped Ce:LiCAF crystal rod in a prismatic mirror geometry

Abstract

The radial distribution of the excitation energy absorbed in a sidepumped Ce:LiCAF crystal rod was measured experimentally and
numerically. The measurements seek to provide qualitative evaluation
of the laser-pumping efficiency in a prismatic mirror design. By illuminating the Ce:LiCAF crystal by the fourth-harmonics of an Nd:YAG laser at 266 nm, we recorded the far-field images of its 290 nm fluorescence using a CCD camera. The relative intensities of the fluorescence patterns represent the ground-state depopulation due to pump laser absorption at each point in the crystal rod. Non-uniform spatial fluorescence pattern was recorded with one-side pumping, in stark contrast to the nearly uniform absorption observed during fourside illumination. The influence of linear absorption on the pump energy distribution was also studied. It was shown that nearly uniform energy distribution, and thereby better pumping efficiency, is possible with four-side excitation than one-side pumping in good agreement with the experimental results.