SPECTRAL HOLE-BURNING STUDY OF SQUARAINE DYES IN POLYMER-FILMS

A study of the hole-burning mechanisms of bis[4-(diethylamino)-2-hydroxyphenyl]squaraine (DEAH) and bis[4-(dielhylamino)-phenyl] squaraine (DEA) in hydrogen-bonding and non-hydrogen-bonding polymers is presented. Intramolecular H-bonding is only possible for DEAH. In all systems, the spectral holes are not persistent and decay with a distribution of rates ranging from 10(-5)s(-1) to about 1s(-1), the time resolution of the experiment. In H-donating matrices, this distribution varies with the burning wavelength. From the hole-burning efficiencies and the kinetics of hole refilling, four different types of non-photochemical hole-burning mechanisms are postulated. The efficiency of these mechanisms depends mainly on the occurrence of processes slowing down the relaxation to the initial product state.