Modified theory of photoinduced molecular polar alignment in azo polymers

An improvement on the simplified theory of all-optical poling [Chem. Phys. Lett. 286, 415 (1998)] is proposed. In this improvement the influence of th e cis isomer is taken into account in the process of photoinduced molecular polar alignment. An analytical expression for the induced polar order in t he steady-state regime is derived. This expression shows that, although the contribution to the photoinduced second-order susceptibility fi om the cis state itself can be neglected, the population of the cis state plays an im portant role. This result suggests the possibility that one can improve the induced polar order by increasing the poling temperature, so that thermal- assisted optical poling can be explained. (C) 2000 Optical Society of Ameri ca OCIS codes: 190.2620, 190.4400, 230.4320.