微下拉法生长Tm:LGGG晶体及其2.0μm激光性能的研究

Having great value of practical application in many key fields such as medicine, environment protection and military affair, the 2.0 μm laser crystal has attracted much attention in recent years and become one of the focuses in the study of functional crystal materials. This project is an effort to study the crystal growth and laser properties of Tm and Lu doped Tm:LGGG crystal which shows high potential in the generation of 2.0 μm laser. As we know, LGGG crystal is a novel host material which owns multi-center structure as a typical garnet crystal; meanwhile, it possesses a disordered structure because of the fractional Lu ion doping. As a result the emission band of the active ion inside is broadened extremely, and this is very favorable for the Q-switched and mode-locked pulse laser generation. In view of the high-speed growth, economic use of starting raw materials and shape designed growth that micro-pulling-down (μ-PD) technology has demonstrated, we have adopted it in the growth of Tm:LGGG crystals in this project. The basic physical properties, especially the spectral properties, of the crystal will be tested. After that, the J-O theory will be applied to calculate the spontaneous transition probabilities, the branching ratio, and the radiative lifetime, so we could understand the effects of the doping levels of Tm and Lu ions on the laser properties. Then we will carry out the laser tests on selected good samples, including the continuous wave, Q-switched and mode-locked pulse laser, so as to obtain a more comprehensive evaluation of the performance of Tm:LGGG crystal in 2.0 μm laser generation.

2.0μm激光在医疗、环保、军事等领域具有重要的应用价值，因此对该波段激光晶体的研究探索成为当前功能晶体研究领域的热点之一。本项目拟针对在2.0μm激光产生方面具有潜在应用的Tm和Lu离子掺杂的Tm:LGGG系列晶体进行研究。LGGG晶体是一种优异的新型激光基质晶体，它具有石榴石晶体的多中心结构，同时Lu离子的掺入使得晶体具有了一定的无序结构特性，因此激活离子在晶体中的光谱有显著的展宽，这非常有利于调Q和锁模脉冲激光的产生。鉴于新型的微下拉晶体生长技术具有速度快、用料少、近尺寸生长等突出优点，我们将采用该技术进行Tm:LGGG晶体的生长。通过对Tm:LGGG晶体的基本物理性质，尤其是光谱性质进行详细表征，以及J-O理论计算，获得Tm和Lu离子掺杂浓度对晶体性能的影响规律。筛选性能较好的样品，并详细研究它们的连续波、调Q及锁模脉冲激光的性能，全面评价该晶体在2.0μm激光产生方面的应用前景。

2.0μm激光在医疗、环保、军事等领域都具有重要的应用价值。本项目采用微下拉法和提拉法相结合的高温熔体技术，开展了系列Tm:LGGG晶体的探索和生长技术研究，获得了高质量的单晶。并对获得的多组分样品进行了室温下和10K下的吸收光谱、荧光光谱、荧光寿命等的研究，对晶体的光谱性质进行了评价。通过加工相应的晶体样品器件，测试了它们的连续激光和调Q激光性质的研究，获得了最大输出功率 140 mW、最大脉冲能量 3.19 μJ、最短脉冲宽度 1.29 μs、最大重复频率 43.9 kHz的激光输出。