Research On The Influence Of Photobleaching Process On Polymer's Second Harmonic Generation And Thermo-Optic Effect

In an Attenuated Total Reflection (ATR) multi-layers configuration, light reflectivity can be highly dependent on layer parameters such as the layer thickness and refractive index. A tiny change in these parameters can lead to a large change in the light reflectivity. The ATR device with plannar structure, is suitable for plannar micro fabrication process and integrition. ATR devices can be significantly enhanced by Surface Plasmon Resonance (SPR) through cladding proper metal film. This characteristic enables the realization of many novel type optoelectronic devices based on this structure.Numerous investigations during past two decades show that ATR techniques are powerful plateform for Optic-electro technology research and Optic-electro device development.Nonlinear polymer films are expected to offer a number of advantages over inorganic crystals, including their relatively large second-order susceptibility, fast response time and simple processing techniques. Recent years, numerous researches focused on NLO polymer synthesis, properties and functional devices fabrication. Polymer optical waveguide configuration, based on ATR techniques and enhanced by SPR, can demonstrate polymer's nonlinear properties and realize prototypic functional devices.Photobleaching is an attractive method for fabricating optical waveguide in polymeric materials. The variation in optical performance and chemical stability of polymer during the photobleaching is an important characteristic for its application in waveguide devices. Photobleaching process can simulate the expedited phenomena of aging and failure of polymer, as well as polymer poling degradation.In the dissertation, the influence of photobleaching process on the thermo-optic coefficient (TOC) of Disperse Red 1/poly(methl methacrylate) (DR1/PMMA) film is also investigated by using the ATR technique. Experimental results show that the absolute values of the thermo-optic coefficient of fully bleached Disperse Red 1/poly(methl methacrylate) film are smaller than those of un-bleached film. Moreover, the absolute value of anisotropy of the thermo-optic coefficient also decreases after the disperse red 1/poly (methl methacrylate) film is fully bleached.In the dissertation, the second-order nonlinearity of poled-polymer during photobleaching process is monitored with Second Harmonic Generation (SHG) intensity enhanced by Surface Plasmon Resonance (SPR) in an Attenuated Total Reflection (ATR) configuration. The nonlinear coefficient d33 of the poled polymer is determined by comparing the SPR enhanced SHG intensities with that from the calibrated quartz. Experimental results show that photobleaching process has less effect on the second-order nonlinearity of a poled cross-linked polymer than that of a poled side-chain polymer. And, the derived mathematical expression for determining the NLO coefficient is much simplified.