| Because of the high brightness and high directivity of the laser sources,the optical storage has gotten a rapid development and formally entered actual application fields since entering the 21 st century.Compared to the magnetic storage and semiconductor storage,optical storage has higher storage density,higher signal-to-noise ratio and can be repeated to wipe,which conforms to the trend of the time and has inestimable prospect.In recent years,organic polymersobtain rapid developmentdue to their large nonlinear optical coefficients,quick nonlinear response rates,high damage threshold and easly modified structure.Thus,many attations have been paid on organic polymers because of their potential applicationsprospects such asmeta-hologram,optical logic gates,two-dimensional spectral sensor,topological insulators,metamaterials and polarization microscopy.As a typical representative of organic polymer materials,when excited with suitanle pump light,the azo materialshave excellent optical anisotropy,which makes azo-containing materials have a great application prospect in the field of nonlinear optics applications.Otherwise,due to the nonlinear nature the two-photon fluorescence has strong penetrating power,the choice of strong motivational,high transverse and longitudinal resolution and reducing the biological tissue to stimulate the light absorption and scattering characteristics,so the modulation of the two-photon fluorescence is interesting and useful.This thesis focuses on theresearch of nonlinear optical applicationsinazo-containing polymers and the modulation of two-photon polarization.In the first section,we describe the history of nonlinear optical applications and focuse on concept and history of photoinduced anisotropic application.Thenwe inducethe mechanism and characteristics of holographic storage and polarization holographic storage,which are among the most important photoinduced anisotropic applications.Compared with the ordinary holographic storage are analyzed,we present the advantages and application prospects of polarization holographic storage.Third we introduce the application of two-photon fluorescence development,analyzes the advantages and disadvantages of two-photon fluorescence in the application and its development bottleneck.Finally the main content of this paper are outlined.In the second section,we introduces the concept and physical nature of the second order and third order nonlinear optical and the application prospect of nonlinear absorption and nonlinear refraction.Then the molecular structure characteristics and the optical properties of azoazobenzene polymers are introduced,particularly the generation mechanism for the photo-cis-trans isomerization of the azo molecules,which shows that the azobenzene polymers have remarkable photoinduced anisotropy and can be ideal optical storage materials.In the third section,we investigate the optical birefringence properties of two azo-containing polymers,and analyze the experimental results in theory.The experimental results show that the stored birefringence in azobenzene liquid-crystalline polymer at room temperature the birefringence of storage is very stable,and after pump the birefringence will relax to a stable value which is a very suitable for polarization holographic storage.Then the intensity of pump light and temperature influence of the photoinduced birefringence are studied.We findthat change the intensity of pump light and temperature can effectively control photoinduced birefringence of the samples,and its mechanism is discussed in this section.In the fourth section,based on the photoinduced anisotropy in azobenzene liquid-crystalline polymer,polarization holographic recordings are accomplished with both orthogonal linear and circular polarizations.Otherwise,two superimposed holograms are stored in the same volume of an azobenzene liquid-crystalline polymer based on double-exposure polarization holographic method.The polarization transformation characteristics were studied through the theoretical calculations and experimental results.The holographic gratings based on double-exposure polarization holographic are found not the simple sum of two separate holographic gratings because the polarization transformation characteristics have changed.Finally polarization-controlled optical image operations were demonstrated based on double-exposure polarization holographic method.Through changing the polarization of the readout beam,we can alter the brightness ratio and the polarization states of the reconstruction image.In the fifth section,optical logical operation,which is an important branch in the field of optical,has several advantages like high interconnectedness and parallelism,high transmission speed and high switching speed.In this section,based on the azo-containing polymers’ different response of photoinduced birefringence tolinearly and circularly polarized pump light we design all optical logic gates,including "AND","OR" and "XOR".In addition,based on double-exposure polarization holographic gratings,optical logicalsummation and subtraction are investigated,and the optical logic gates "OR" and "XOR" are designed.In the sixth section,polarization control,acted as a new kind of optical device,can control some special nonlinear process.In this section,we studied the fluorescence polarization modulation characteristics of two fluorescent materials.The peak fluorescence intensity versus the input irradiance was measured to meet a square dependence,which offered an evidence for two-photon excited fluorescence.It is found that the variations of the two-photon excited fluorescence intensity showed strong an obvious change when the polarization of incident lights changes from linear polarization to circular polarization and tightly dependent on the linearly polarized component of the incident light and modulation efficiency will have changesif some external factors have changes.Combination with the characteristics of two-photon absorption and excited state absorption,the change of polarization modulation efficiency are discussed in detail. |
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