Periodic oscillation of the optical transmittance in azo dye-doped liquid crystals between two crossed polarizers

The periodic oscillation of the optical transmittance in the nematic liquid crystals (5CB) doped with azobenzene compound (DR1) between two crossed polarizers has been demonstrated and investigated by monitoring the signal intensity variation of the transmitted light in different conditions of the light irradiation and environment temperature. It is found that the oscillation of the transmittance lasts more than 4 periods before the nematic-isotropic phase transition when the dye doped liquid crystal sample is heated from 20 to 40 degrees C. The oscillation is attributed to the continuous decrease of the birefringence of the dye doped liquid crystals with the temperature increasing. The oscillation curve shifts forward significantly when the sample is exposed to the pump light irradiation, which indicates that the pump light irradiation induces an additional decrease of the birefringence. A more accurate and comprehensive way for estimating the magnitude of the birefringence of the anisotropic materials is proposed based on the transmittance oscillation phenomenon. The switchable properties and the potential applications of the transmittance oscillation are discussed.