基于复合材料的IG模式可控被动调Q微片激光器研究

Ince-Gaussian (IG) laser beam has been widely used in molecular manipulation, formation of optical vortex, material microstructure analyzation and reconstruction. Theoretical design, fabrication and performance of composite crystals based on Nd3+ ions doped crystals and Cr4+:YAG crystal are proposed in this project. The key parameters of concentration, thickness of Nd3+ ions doped crystals and Cr4+:YAG crystal in composite crystals will be investigated for constructing highly efficient, high peak power, IG modes controllable passively Q-switched microchip lasers. The effects of pump beam shape, beam diameter, incident angle and incident pump intensity of laser-diode on the direct generation of the tailored IG modes in passively Q-switched microchip lasers based on composite crystals will be systematically studied. The key issues of direct generation of IG mode in composite crystal passively Q-switched microchip lasers are addressed. Based on the relationship between IG modes generation and the concentration of Nd3+ ions and Cr4+ ions in the composite crystals, the ratio of the Nd3+ ions doped crystal to the Cr4+:YAG crystal, the mechanics of direct generation of IG modes in composite crystal passively Q-switched microchip lasers is given by applying the paraxial wave equation in elliptic coordinates. The investigation will provides a solid foundation on theory and experimental data for developing highly efficient, high peak power, IG modes controllable passively Q-switched microchip lasers based on composite crystals.

Ince-Gaussian（IG）激光在生物分子操控、光学漩涡阵列、材料结构微观分析与重组等方面有非常广阔的应用潜力。本项目拟通过开展基于掺Nd3+离子晶体与Cr4+:YAG晶体的复合晶体的理论设计、制备及性能研究，获得实现高光学转换效率、高峰值功率、IG 模式可控微片激光器所需的复合激光晶体的掺杂浓度、晶片厚度等关键参数。系统研究激光二极管泵浦光的光斑形状、大小、入射角度与光强对复合激光晶体被动调Q微片激光器直接产生IG模式可控激光输出的影响，解决复合晶体微片激光器直接产生IG模式可控激光输出的关键问题。结合复合激光晶体中Nd3+离子和Cr4+离子掺杂浓度、厚度配比与IG模式激光输出之间的内在联系，利用傍轴波动光学方程，从理论上揭示被动调Q微片激光器直接产生IG模式激光输出的物理机制。为今后推动基于复合材料的高光学转换效率、高峰值功率、IG模式可控微片激光器的发展提供理论依据和实验数据。

Ince-Gaussian（IG）模式高峰值功率脉冲激光在生物分子操控、光学漩涡阵列、材料结构微观分析与重组等方面有非常广阔的应用潜力。资助项目系统地研究了激光二极管倾斜泵浦光参数对Nd:YAG/Cr4+:YAG、Nd:YVO4/Cr4+:YAG等被动调Q微片激光器直接产生LG、IG和HG模式可调控激光输出的影响，阐明了倾斜泵浦打破被动调Q微片激光器增益分布对称性从而实现IG模式激光输出机理。在倾斜泵浦的Cr,Nd:YAG自调Q微片激光器中获得了平均输出功率高达2 W的高阶IG模式激光输出，而且光学转换效率高达30%。在Nd:YVO4/Cr4+:YAG被动调Q微片激光器中通过调节泵浦光焦点在Nd:YVO4晶体中的位置实现了LG、IG和HG模式激光的输出。而且通过调整泵浦光斑的大小和在晶体中的位置实现了高阶HG模式激光的可调控输出。获得了线偏振泵浦光对Nd:YVO4/Cr4+:YAG被动调Q微片激光器实现IG模式取向和模式同时调控的方法。创新性地采用偏心高斯泵浦光作为泵浦源，在Cr4+:YAG被动调Q的微片激光器中获得的高光学转换效率LG、IG和HG模式可调控脉冲激光输出，阐明了准直聚焦透镜偏移量对偏心高斯光束的光斑形状和倾斜角度的影响。获得了在偏心高斯光束泵浦的Nd:YAG/Cr4+:YAG被动调Q微片激光器中实现了LG、IG和HG模式激光的高光学转换效率激光输出所对应的准直聚焦透镜的偏移距离，对于研制模式可调控高峰值功率被动调Q微片激光器起到了极大的促进作用。利用空心光聚焦透镜实现的紧聚焦环形光作为泵浦光，在Nd:YAG连续微片激光器中实现了径向与角向偏振可转换的高光束质量涡旋激光输出，而且在Cr,Nd:YAG自调Q微片激光器中实现了螺旋相位恒定的涡旋脉冲激光输出，极大地拓宽了集成化微片激光器的应用领域。利用Yb:YAG晶体较宽的发射光谱和YVO4晶体的受激拉曼散射特性构建了Yb:YAG/YVO4拉曼微片激光器，实现了输出功率为1.16 W、光学转换效率为18.4%、携带光频梳的涡旋阵列激光输出。通过该项目的研究，共发表学术论文27篇，其中SCI收录19篇，EI收录5篇。出版学术专著1部。申请国家发明专利6项。参加学术会议13人次。培养博士研究生7人，其中已毕业3人；培养硕士研究生12人，其中已毕业9名。研究生获得国家奖学金3人次，获得福建省优秀硕士论文1篇。