Action of the 216-nm fifth harmonic of a Nd:YAP laser on photosensitive germanosilicate glass films

The absorption spectrum, refractive index, and relief of the surface of a germanosilicate glass film are studied upon the non-destructive action of the 216-nm (5.75-eV) fifth harmonic of a repetitively pulsed Nd:YAP laser. It is shown that laser irradiation of films induces a strong photorefractive effect despite the relatively low absorption coefficient. For the 100-mJ cm^-2 energy density and above, two-photon process make a noticeable contribution to the absorption of laser radiation at 216 nm. The diffraction efficiency of photoinduced phase gratings achieved ~7 × 10^-3 for the exposure dose ~6 kJ cm^-2, which corresponds to the induced refractive index 1.5 × 10^-3. At higher exposure doses, a relief appears on a film surface and the diffraction efficiency of a phase grating is reduced.