29 October 1998 Optical nonlinearity and multiplex holographic storage in azo side-chain liquid crystalline polymer
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Abstract
Optical nonlinearity and multiplex holographic storage using azo side-chain polymer are studied by using degenerate four- wave mixing and polarized pump-probe laser method. The He-Ne excitation laser wavelength is located at the tail end of the absorption peak of the sample. This material shows high grating diffraction efficiency and promises information storage capability using weak absorption. The diffraction efficiency of the grating is up to the order of 10-2. The effect of input beam polarization planes on grating is studied. The diffraction grating efficiency is lowest when the polarization of the redout beam is orthogonal to that of both writing beams. An angle multiplex holographic storage study is also performed in the sample. Information can be stored for a long time at room temperature. The information readout of this multiplex holographic storage system can be controlled by the polarization state of the readout beam. Dependence of grating diffraction efficiency on the sample temperature is studied. It is demonstrated that the higher the temperature under the melting temperature of the sample, the higher the diffraction efficiency and the faster the relaxation time of the grating. The grating is completely erased by increasing the temperature over the melting temperature of the sample. Reading the grating with a circularly polarized light does not erase the grating. When two recording beams are turned off, a large part of the grating remains for a long time and only a small part of the grating degrades. The results show that the azo side-chain polymer is a good information storage material. The anisotropic optical nonlinear refractive index of the sample is also measured. The relationship of the nonlinear refractive index of the samples, the different ratios of azo functional groups in the polymers, and the temperature of the sample are also studied. The highest nonlinear refractive index is up to the order of 10-2. The optical nonlinearity of the samples increase with increasing sample temperature. No anisotropic nonlinearity appears when the temperature of the sample is over the melting temperature of the sample. The anisotropic nonlinearity levels of three samples with different azo side-group ratios in the polymer are compared.
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Xinxian Bao, Xinxian Bao, Chunfei Li, Chunfei Li, Yanqing Tian, Yanqing Tian, William M. Tong, William M. Tong, "Optical nonlinearity and multiplex holographic storage in azo side-chain liquid crystalline polymer", Proc. SPIE 3474, Second-Order Organic Nonlinear Optics, (29 October 1998); doi: 10.1117/12.328575; https://doi.org/10.1117/12.328575
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