| Optoelectronic technology has been developed rapidly because of the varieties of inquries in industrial field and people's life. Optoelectronic material is a vital part in this technology. Among all kinds of materials, crystals are one special kind and the fabricating processes of crystals such as growth, cutting, polishing and coating are attracting much attention, In this thesis, we focus on one special kind of optoelectronic crystal, i.e. the composite crystal or the diffusion-bonded crystal. This kind of crystals is accomplished through diffusion-bonding laser gain crystals and the undoped or pure substrates. The undoped part plays a role as heat sink, which will benefit to heat diffusions. This design can effectively decrease the thermal gradient from central part to the side surface of the crystal. For example, under the same pumping conditions, the maximum temperature gradient can be decreased by 23.4% if Nd:YV04 is substituted by the composite YVO4/Nd:YVO4 crystal. The composite crstal can weaken the thermal lens effect caused by end-surface bulge and temperature gradient, which will make the laser operate more stablely and efficiently. Meanwhile, larger size crystal can be obtained form the diffusion-bonding technique. This will solve the problem that some high-performance crystal can not be grown to large size. And, the composite crystal can do benefit to laser optimization, i.e. realization of compact and integral lasers, which will play important role in passively Q-switched lasers.High performance can be obtained from laser gain crystals through the diffusion-bonding technique. We study the fabricating technique and laser performances of the diffusion-bonded crystals in order to find their advantages and disadvantages. This will help us optimize lasers and obtain high output power and high beam quality.In this thesis, we investigate the composite laser crystals in detail, e.g. growth of rough crystal, processing of rough crystal, processing of composite crystal, laser performance study of composite crystal. The main contents of this dissertation are as follows:1. The growth technique for rough Nd:YVO4 and Nd:YAG crystals are investigated. The processes include the synthesis of polycrystalline raw materials, growth of single crystals, temperature reducing, annealing and quality evaluation of the rough crystals, etc. And several high quality Nd:YV04 and Nd:YAG single crystals are grown during the period of this thesis.2. The fabricating technique for composite Nd:YVO4 and Nd:YAG crystals are investigated, including rough crystal selection, cutting, coarse grinding, polishing, rough crystal quality detection, optical bonding, temperature raising, bonding surface detection, coarse grinding of composite crystal, polishing of composite crystal, surface detection of composite crystal, coatings, detection of coatings, etc. And several high quality composite crystals are fabricated during the period of this thesis, including single-end bonded YVO4/Nd:YVO4, YAG/Nd:YAG crystals and double-end bonded YVO4/Nd:YVO4/YVO4 crystals.3. We experimentally studied the effects of composite crystals in weaken the thermal effect and improve laser performances. Composite YAG/Nd:YAG crystal is employed to generate 1123 nm laser, which was compared with undoped Nd:YAG 1123 nm lasers. Single-end bonded YVO4/Nd:YVO4 crystals are used to generate 1064 nm and 1085 nm lasers. Effective thermal focal lengths of diode-end-pumped single-end bonded YVO4/Nd:YVO4 crystal are measured. With a single-end bonded YVO4/Nd:YVO4 crystal as the laser gain medium, we realize intracavity KTiOAsO4 (KTA) optical parametric oscillator (OPO) and obtain high-conversion-efficiency mid-infrared output. And we study the laser performance of double-end bonded YVO4/Nd:YVO4/YVO4 crystals. In the experiments, diode double-end pumping scheme is adopted to increase the output power. The experimental results are analyzed.The main innovations of this dissertation are as follows:1. Composite YAG/Nd:YAG crystal is employed to generate 1123 nm laser for the first time and the laser performance is improved especially in long cavities.2. Single-end bonded YVO4/Nd:YVO4 crystal is pumped by an 880 nm LD to generate 1085 nm laser.3. Single-end bonded YVO4/Nd:YVO4 crystal is adopted as the laser gain medium to pump intracavity KTA-OPO for the first time. And high conversion efficiency is obtained. |
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