Photothermal Conversion of Color Centers in $$\hbox {CaF}_{2}$$ CaF 2 Crystals: A Process Underlying the Use of Crystals as a Holographic Medium

Abstract

Photothermal effects in a holographic medium of calcium fluoride crystals with color centers (CaF 2 ) are discussed. It is shown that photochromism of this crystal makes it possible to record volume holograms within its volume and to change their physical properties by photothermal treatments. The diffusion-drift mechanism of a hologram recording in CaF 2 includes the conversion of centers and their redistribution over the crystal bulk. Depending on the readout wavelength, it is possible to read out amplitude, amplitude phase, or phase holograms. The opportunity to record thick holograms in CaF 2 and their high resistance with respect to non-coherent illumination at an elevated temperature allows forming narrow-band angular and spectral holographic filters in CaF 2 .