Laser-induced changes in optical properties of H4TPP2+ doped silica gel prepared by sol–gel method

Optical absorption and photoluminescence of diacid tetraphenylprophyrine, H4TPP2+, species in silica gel glass prepared by the sol–gel (SG) method were measured in the 350–800 nm range. Under continuous (CW) laser excitation the characteristics of thermal lensing (TL) were measured at room temperature, under resonant and non-resonant conditions. Our results are analyzed based on a theoretical model for CW laser-induced thermal lensing, under a Gaussian-beam approximation. The effects of the power input and the response time for TL are explained in terms of the coupling of the H4TPP2+ molecules to the local vibrations, for resonant excitations. Also, the observation of laser-induced permanent changes in the refractive index of our glass sample under resonant and non-resonant excitations is reported and discussed.