THz QCL波导结构研究与光束质量分析

Research on waveguide structure and analysis of beam quality of THz QCL

THz量子级联激光器是理想的固态THz源,研究波导结构对激射光特性和远场光束质量的影响,是THz QCL设计中的关键。本文采用有限元方法对THz QCL双面和单面金属波导结构的限制和损耗特性进行分析,给出了限制因子、波导损耗和阈值增益随波导结构、激射波长等参数的变化关系。仿真实验结果表明:与单面金属波导相比,双面金属波导对光具有更好的限制作用,损耗也比较小,更适合做有源区的波导限制结构。在计算出波导中光场分布的基础上,又利用矢量衍射理论分析了THz QCL的光束质量,给出了不同波导宽度时出射光束的远场光束宽度和远场发散角,从应用方面为QCL的设计提供了一定参考。

THz Quantum Cascade Laser（QCL） is an ideal solid-state THz source.It is an important part of THz QCL design to investigate the influence of waveguide structures on the properties of lasing light and beam quality.The confinement and loss properties for double-metal and single-metal waveguides of THz QCL are analyzed using finite element method.The dependence of confinement factor,waveguide loss and threshold gain on the waveguide structure,the lasing wavelength and other parameters is presented.The results show that compared with the single-metal waveguides,the double-metal waveguides have better light confinements and lower losses,so they are more suitable for waveguide confinement of active region.Based on the calculated light field distribution in the waveguides,the beam qualities are analyzed using the vector diffraction theory.Far-field beam widths and divergence angles for different waveguide widths are given,which has provided a helpful reference for QCL design from application perspective.