Cr～（4+）：YAG作为被动调Q开关和激光增益介质的研究

【作者】 吕凤萍；

【导师】 王加贤；

【作者基本信息】 华侨大学 ， 物理电子学， 2003， 硕士

【摘要】 Cr⁴⁺∶YAG晶体作为近年来人们发现的新型固体激光材料，具有吸收截面大、可饱和吸收稳定性好、热传导性和机械性能良好等优点。本论文基于Cr⁴⁺∶YAG晶体既可以作为Nd∶YAG激光器的被动调Q开关、又可以作为激光增益介质的特点，采用理论和实验相结合的研究方法，详细而具体的研究了Cr⁴⁺∶YAG晶体被动调Q、调Q倍频和双波长激光输出的特性。 第一章：介绍了Cr⁴⁺∶YAG的光学性能、国内外研究概况和本论文研究的主要内容。Cr⁴⁺∶YAG晶体优良的物化性能，使它作为被动调Q开关和激光增益介质已实现了不同种类的调Q和锁模运转。 第二章：从速率方程出发，研究了Cr⁴⁺∶YAG晶体的调Q特性。在光强不太大的情况下，Cr⁴⁺∶YAG可作为慢饱和吸收体，其初始透过率越靠近最大初始透过率，损耗调制越大。在平-凸非稳腔中，采用初始透过率为30％和63％的Cr⁴⁺∶YAG进行实验，得到能量和脉宽相应为52mJ、8ns和45.7mJ、18ns的调Q脉冲输出，这表明：采用初始透过率越靠近最大初始透过率的Cr⁴⁺∶YAG，可得到越理想的实验结果，这与理论分析一致。此外，还分析了Cr⁴⁺∶YAG在平-凸非稳腔中的位置、激光器结构和参数对Nd∶YAG激光器调Q脉冲输出的影响。 第三章：采用CLBO对Cr⁴⁺∶YAG调Q Nd∶YAG激光器进行腔内倍频，得到了不同谐振腔中的绿光脉冲输出。理论上分析了影响倍频转换效率的几个因素，分别在平凹腔和双凹腔Nd∶YAG/Cr⁴⁺∶YAG被动调Q激光器中插入CLBO进行实验研究，得到了转换效率分别为33.5％，46.8％的绿光脉冲输出。双凹腔中倍频转换效率高的原因是双凹腔中CLBO晶体处于基波光束光腰处，该处光束半径小，光束发散角小。 第四章：设计了一个复合腔，使Cr⁴⁺∶YAG作为可饱和吸收体对1.06μm激光调Q的同时，又作为激光增益介质产生1.44μm激光，在国内首次得到1.06μm和1.44μm双波长激光输出，并对1.44μm激光脉宽进行了理论分析。1.06μm和1.44μm激光脉冲的能量和脉宽分别是18mJ、52ns和0.2mJ、19ns，并采用Cr⁴⁺∶YAG晶体的相关参数，从理论上计算了1.44μm激光的脉宽，理论结果和实验结果基本一致。更多还原

【Abstract】 As a new solid laser material in recent years, Cr4+:YAG crystal has super advantages, such as big absorption cross section, stable saturable absorption, good heat-conducting and mechanical performance. With the theoretical and experimental methods, the characters of Cr4+:YAG are studied from Cr4+:YAG as passive Q-switching in Nd:YAG laser, intracavity frequency-doubling of Q-switching laser and dual-wavelength laser, which is based on Cr4+:YAG’s operations of saturable absorption and laser gaining medium.Chapter 1: Introducing the Cr4+:YAG’s optical function, the general research situation and the main idea of this thesis. The Cr +:YAG crystal has been operated differently as passive Q-switching and mode-locking medium by researchers at home and abroad.Chapter 2: Researching the Q-switching performance of Cr4+:YAG crystals with the rate equations. In low laser intensity, Cr4+:YAG can be used as slow saturable absorber. The nearer is the initial transparence to the max initial transparence, the bigger is the loss modulation. The experiment with Cr4+:YAG of 30% and 63% initial transparence was conducted in plane-convex unstable resonators and get the laser’s FWHM and output energy are accordingly 8ns and 52mJ, 18ns and 45.7mJ. It is proved that the nearer the max initial transparence is the initial transparence, the stronger intensity and smaller FWHM can be obtained Cr4+:YAG crystal, which is consistent with the theoretical results. In addition, the experimental results acquired in different resonator structures and parameters are also analyzed.Chapter 3: Researching the intracavity frequency-doubling of Nd:YAG/Cr4+:YAG Q-switching laser with CLBO crystal. The several factors to affect the frequency doubling conversion efficiency are analyzed theoryretically. The 33.5% and 46.8% frequency doubling conversion efficiency are achieved in plane-concave and dual-concave resonators. The former value is clearly smaller than the latter, because the laser beam radius and the laser beam angle of divergence on the CLBO in the plane-concave resonator is bigger than in the dual-concave resonator.Chapter 4: For the first time achieving the dual-wavelength laser of 1.06m and 1.44m in the designed compound resonator in domestic. The Cr4+:YAG is operated as saturable absorber and laser gaining medium simultaneously. The output energy and FWHM of 1.06 m and 1.44m are 18mJ, 52ns and 0.2mJ, 19ns. The theoretical FWHM of \A4jum laser, which is analyzed theoretically with the pertinent parameters of Cr4+:YAG crystal, is consistent with the experimental results.更多还原