Optical spectroscopy of the (F⁺²)H centre in alkali halide crystals
Methods of production and optimisation of (F⁺²)H centres in alkali halide crystals have been evaluated with particular reference to these centres in oxygen-doped NaCl crystals. Additionally, a laser cavity has been designed and constructed for use with this material. In order to produce (F⁺²)H centres in NaCl, three main processes are involved: additive colouration, annealing, and a two-stage photoaggregation process. Each of these is discussed and the optimum conditions for each are given. A spectroscopic analysis of the final crystals is then performed with a view to understanding the formation kinetics of the (F⁺²)H centre. This work employs low tempeature emission spectroscopy and polarised luminescence and absorption measurements to evaluate the influence of auxiliary F-band light on the laser operation. Comparisons are drawn between these results involving the excited state transitions of the (F⁺²)H centres and the model obtained by Luty et al. in KC1. The crystals produced in this work have been used in the colour centre cavity designed and to date spikes of laser emission have been obtained.