Holographic characteristics of calcium fluoride crystals in the IR region

It is shown that narrow-band transmissive and reflective holographic filters for the near- and mid-IR spectral region can be recorded in calcium fluoride crystals with photochromic color centers. It is established that the diffusion-drift hologram-recording mechanism can provide close to 100% spatial modulation of the color-center concentration. Based on the measured absorption spectra of the crystal, the dispersion of its refractive index in the indicated spectral range is estimated by means of the Kramers-Kronig relations, and the characteristics of transmissive and reflective holograms are calculated. It is concluded that the diffraction efficiency of such holograms can be increased by increasing the concentration of color centers formed in the calcium fluoride crystal at the additive-coloration stage. (C) 2015 Optical Society of America.