| Nonlinear optics (NLO) is an important branch of nonlinear physics and modern optics, and is also one of basic theories of photonics. It concerns varied effects of materials under the laser, which is helpful to understand the generation, transfer and storage of photon information. Organic NLO material has very important application because of its large nonlinearity, fast response, low cost, and flexibility of molecule design. For example, Organic NLO material has been used in THz laser generator and high performance electro-optic devices. However, high performance organic NLO devices with high thermal stability are still great challenge. From the last 80's to the 90's, organic salts, especially for stilbazolium derivative, have become an attractive NLO material. In one hand, the nonlinearity of ionic chromophores can be improved by optimized molecule design; on the other hand, by introducing different counter-ions, the crystal structure can be adjusted for given NLO applications, so it is possible to find better NLO material in organic salts.This work is based on traditional stilbazolium salts, and proposed to design new stilbazolium-liked structure using carbazole to form one dimension intramolecular charge transfer (1DICT) and two dimensions intramolecular charge transfer (2DICT) system. Their linear and second-order nonlinear optical properties are studied; by ion-changing method, different counter-ions are introduced to explore the counter-ion effect on crystal structure. At the same time, the two-photon absorbing property has been characterized and one of 2DICT salts has been used successfully as initiator in two-photon induced polymerization micro-fabrication with good performance.The whole paper consists of eight parts and the main point of each part is listed as follows:Chapter 1: As an introduction, this chapter discussed background of nonlinear optics (NLO) and nonlinear optics material. It covered the development and basic physics theory of NLO, theory model of organic NLO dyes, and guideline of molecule design and research progress. Finally, we addressed the purpose, significance and contents of this work.Chapter 2: Introduce the reagents, equipment and measurement motheds used in this work.Chapter 3: This chapter introduces linear optical properties of 1DICT/2DICT compounds, including UV spectrum, fluorescence spectrum, fluorescence quantum yield and lifetime of excited state. At same time, some information of molecule orbits and excited state property have been provided with the result of quantum chemistry calculation. All these information will be the basic data for further understanding their NLO properties.Chapter 4: In this chapter, molecule second-order NLO coefficient of one 2DICT compounds has been measurened by Hyper-Rayleigh scattering (HRS) method.Chapter 5: In this chapter, different anions have been introduced into carbazole based stilbazolium salts, and the thermal stability and NLO activity also be checked. The single crystals of NLO active compounds have been obtain. By the comparing the crystal structure, the counter-ion effect on crystal structure has been analysed.Chapter 6: The two-photon absorption (TPA) property of 1DICT/2DICT compounds has been discussed in this chapter. 2DICT compounds has high TPA cross-section (>1700GM) at 800nm, which can be attribute to interaction of two ICT. Some 3D photonic crystal obtained from two-photon induced polymerization micro-fabrication with 2DICT compounds as initiator.Chapter 7: The conclusions were drawn in this chapter. Chapter 8: Experimental part including measurement and synthesis.
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