Influence of temperature on the relaxation kinetics of spontaneous pattern formation in an azo–polymer film

The relaxation dynamics of photoinduced spontaneous surface relief gratings (SRG) printed on an azo polymer films has been investigated using pulsed exposure. The λ=532 nm line of a diode-pumped solid-state (DPSS) laser is used as an inscription beam. The formation of spontaneous SRG is monitored using the intensity of the diffracted beam of a He–Ne laser (632.8 nm). By switching off the recording beam, a sharp enhancement occurs, that is followed by a slow relaxation process. Surprisingly, by switching on the writing beam, a sharp decrease occurs, that is followed by an increase under further illumination. These sharp variations strongly depend on the temperature. The temperature dependence of spontaneous SRG formation is presented. The orientation and motion mechanism of azo–chormophores is enhanced by thermal effects. However, at temperatures around Tg glass transition, the mass transport vanishes.