Spectral hole-burning studies of nile red and cresyl violet in polyvinylbutyral and polyvinylformal films have been performed. From the shape of spectral holes under the influence of an electric field, the dipole moment difference between the ground and excited state of both dyes has been determined. The Stark effect was investigated at different positions in the inhomogeneously broadened absorption band of the guest molecules. The observed dipole moment difference decreases with increasing wavelength. This variation is caused by the matrix induced dipole moment. For nile red, which is a neutral and polar molecule, the distribution of induced dipole moments is strongly correlated with the orientation of its ground state dipole moment. In the case of cresyl violet perchlorate, which is a salt, this distribution is anisotropic for guests absorbing in the blue part of the inhomogeneous band but becomes more isotropic as the absorption wavelength increases. The wavelength dependence of the observed dipole moment is much stronger and is ascribed to the existence of the cresyl violet perchlorate salt in different states of solvation.

The observatiqn of photon-gated hologram formation in a boric acid glass doped with triphenylene is reported. The first photon excites triphenylene to its first singlet excited state and, through intersystem-crossing, populates the first triplet stateTI. The second photon excites TI to T,, where autoionization occurs, leading to the formation of a radical cation. The gatinglight populating TI via SI is spatially uniform, while the light exciting TI to T, is spatially modulated. The long lifetime of the first triplet state allows Recording with low light intensities (mW/cm2). The spatially modulated excitation light forms three gratings (educt, intermediate state, and product). The extent of the interaction between these gratings depends on the overlap between educt, intermediate, and product absorption and refraction spectra as well as on the reading wavelength. The holograms were read at 363.8 and 632.8 nm. When the gating light is blocked, the holographic efficiency stays constant when read at 632.8 nm but increases substantially when read at 363.8 nm.