Spectral profile of the two-photon absorption coefficients in CaF2 and BaF2

Two-photon absorption spectra due to the valence excitons in CaF2 and BaF2 have been measured using the second harmonic of the output of a XeCl-excimer-laser pumped dye laser as a light source. The band gap energies of CaF2 and BaF2 are obtained as 11.8 and 10.6 eV at 298 K, respectively. The two-photon absorption coefficient beta in the spectral region below the 2P exciton is expressed by an exponential function of the photon energy in both crystals. The values of beta at the 2P exciton peak are about 2x10(-9) cm/W for CaF2 and 3x10(-9) cm/W for BaF2. (C) 2002 American Institute of Physics.