Local Field Enhanced Third-order Nonlinear Optical Properties And All-optical Modulation Of Metal Composite Nanostructures

Probing into the excellent third-order nonlinear optical materials, new structure and researching third-order nonlinear optical properties are all along a very actively advancing task. The interactions of the light and metal composite nanostructures generate new phenomena and realize new function, which has potential applications in the nano-optics field. The main works aim at the development of nonlinear surface plasmon photonic devices on the basis of near-field optics and nonlinear optics, and involve the research of metal composite nanostructures' novel optical phenomena by the effective medium theory and the decoupling approximation, the enhanced optical nonlinearity of metal composite nanostructures and the all-optical modulation based on ATR structure. The main research works and conclusions are as following:1. Optical properties of different shape metal nanoparticles are simulated by the discrete dipole approximation (DDA) method. The effects of the size, the ratio of long-short axes, the surrounding medium on the extinction spectra of spherical silver nanoparticle and gold nanorod are analyzed and the near-field distributions are shown. From the single nanoparticle to multi-nanoparticles system, the coupled dipoles equation method is used to analyze the interaction of many metal nanoparticles, providing well theoretical thought for the experiment.2. Linear optical properties and the effective nonlinear optical properties of metal nanoparticle composites with different volume fraction are investigated by the decoupling approximation. Combining the spectral representation and the Maxwell-Garnett method is to analyze the influence of different structure parameters on the optical bistability of metal nanoparticle composites. The enhanced optical nonlinearity of metal-nonlinear medium multilayer structure under the excitation of surface plasmon polariton is analyzed by the model-field theory and the numerical method, which lay a good foundation of the theory for the realization of all-optical devices.3. A new preparation is used for high concentration and well-dispersion silver nanoparticle polymer composites, which is the combination of Reversible Addition-fragmentation Transfer method and the in-situ reduction, simultaneously. Utilizing the Z-scan experimental setup, the influences of various silver concentration and different matrix composites on the third-order nonlinear optical effects of silver colloidal solutions, Ag nanoparticle doped azo polymer films and Ag nanoparticle doped R6G/PMMA film are investigated. The experimental results demonstrate the addition of Ag nanoparticles can effectively modulate the linear and nonlinear optical properties of metal nanoparticle composites, which is important to the application of new photonic devices.4. All-optical modulations based on ATR structure of azo polymer are investigated, which possess the quicker modulation time, the bigger modulation range and the higher modulation contrast in comparison with the traditional azo polymer one. A new sensitive all-optical modulation project on surface plasmon is proposed, which is very instructive for the new type all-optical modulation.Highlights of the dissertation are as following:1. Optical properties of single nanoparticle and multi-nanoparticles system are investigated by DDA method and the coupled dipoles equation method. The effects of the shape, the size, the ratio of long-short axes, the surrounding medium on the extinction spectra and the near-field distribution are analyzed.2. The enhanced optical nonlinearities are investigated from the random structures to the ordered structures. The effective nonlinear optical properties of metal nanoparticle composites with different volume fraction are investigated by the decoupling approximation. The enhanced optical nonlinearity of metal-nonlinear medium multilayer structure under the excitation of surface plasmon is analyzed, which is beneficial to the application of the multilayer structure.3. A new preparation is used for high concentration and well-dispersion of silver nanoparticle polymer composites. Utilizing the Z-scan experimental setup, the influences of various silver concentration and different composites on the third-order nonlinear optical effects of silver nanoparticle polymer composites are investigated. The experimental results demonstrate the addition of Ag nanoparticles can effectively modulate the linear and nonlinear optical properties of the composites, which is important to the application of new photonic devices.4. All-optical modulations of azo polymer based on ATR structure are realized, which possess the improved modulation effects in comparison with the traditional azo polymer one. A new sensitive all-optical modulator project on surface plasmon polariton is numerical designed. The theoretically analyses possess the instructive meaning for designing new type all-optical devices.