Circularly polarized light-excited all-transverse orientational hole burning and induced anisotropy in azo dye doped polymer films

An original polarimetric experimental setup is used to pump and probe photosensitive films. Photo-induced behavior of Azobenzene Disperse one (AZD1) doped Poly(Methyl MethAcrylate) (PMMA) using both linear and circular polarized light is studied. The anisotropy is not erased by the circular polarization light. The circular polarization light combined with relatively long lifetime of the cis state in doped polymers appears as if it activate all transverse directions of the angular hole burning through the film inducing anisotropy. Under circular polarized light, there is no preferred orientation within the film plane, trans species reorients in the propagation direction of the pump beam. The polarization state of the probe beam after propagation through the pumped film depends strongly on the angle of incidence of both pump and probe beams on the input face. In the case where circular polarized pump and probe beams are under the same angle of incidence, the probe beam “sees” anisotropic film as if it is isotropic. This work shows the possibility to reorient azobenzene-type molecules in two orthogonal directions using alternately linearly and circularly polarized beams.