基于自感应透明效应的被动锁模太赫兹量子级联激光器研究

Terahertz technology plays important roles in communication, imaging, astronomy and dynamic spectroscopy. Terahertz quantum cascade laser is an important small-size terahertz source, but it is difficult for terahertz quantum cascade laser to generate ultrashort terahertz pulse. The passively mode-locked terahertz quantum cascade laser hasn’t been realized. This project first proposes the way to develop passively mode-locked terahertz quantum cascade laser based on self-induced transparency effect and studies the key technologies of ultrashort pulse terahertz quantum cascade laser. This project will establish the new dynamic model for terahertz quantum cascade laser based on quantum transmission line modelling method and study the self-induced transparency effect during the terahertz short pulse propagation in the quantum cascade structure. The terahertz quantum cascade absorber with self-induced transparency effect will be designed and developed by suppressing the longitudinal phonon scattering. Furthermore, the two-section coupled-cavity structure is used to design the passively mode-locked terahertz quantum cascade laser. The bias currents are optimized to enable the electrically isolated two-section active region work in the terahertz quantum cascade gain region and the self-induced transparency resonant absorption region. The designed passively mode-locked terahertz quantum cascade laser will be developed. The project will first successfully realize the passively mode-locked terahertz quantum cascade laser based on the self-induced transparency effect, which will promote the research development of terahertz pulse generation technology.

太赫兹技术在通信、成像、天文学及动态光谱学等领域具有重要应用。太赫兹量子级联激光器作为重要的小体积太赫兹源，如何产生超短太赫兹脉冲一直是研究难点，被动锁模至今没有实现。本项目首次提出基于自感应透明效应研制被动锁模太赫兹量子级联激光器，开展超短脉冲太赫兹量子级联激光器关键技术研究。项目将基于量子传输线模拟方法建立新的太赫兹量子级联激光器动态模型，研究太赫兹短脉冲在量子级联结构中传递的自感应透明效应。通过抑制纵向声子散射，设计并研制具有自感应透明效应的太赫兹量子级联吸收结构。并进一步设计两段式耦合腔被动锁模太赫兹量子级联激光器结构，优化偏置电流使电隔离的两段有源区分别工作在太赫兹量子级联增益区和具有自感应透明效应的共振吸收区，研制被动锁模太赫兹量子级联激光器。项目将首次基于自感应透明效应成功实现被动锁模太赫兹量子级联激光器，有效促进太赫兹脉冲产生技术研究的发展。

太赫兹量子级联激光器具有功率高、体积小、可集成等优点，是重要的太赫兹半导体激光源。开展太赫兹量子级联激光器研究对于推动太赫兹技术在通信、医疗、安全、超快光谱等领域应用具有重要意义，太赫兹量子级联激光器如何产生超快短脉冲一直是领域内研究难点，被动锁模至今未实现。本研究结合量子传输线模拟方法和速率方程，建立了太赫兹量子级联激光器模型，分析了太赫兹量子级联激光器时频域输出特性，将仿真结果与实验结果比较，发现模型能够较为准确仿真太赫兹量子级联激光器输出特性。基于理论模型研究了太赫兹短脉冲在量子级联结构中传输的自感应透明效应，设计并制备了太赫兹量子级联吸收结构，实验测量发现研制的太赫兹量子级联吸收结构在低电压偏置条件下可以实现太赫兹波有效吸收。在理论模型构建、太赫兹量子级联吸收结构研制基础上，进一步研究了锁模太赫兹量子级联激光器，并采用光子晶格波导结构有效抑制输出谱边模，实现输出模场调控。本研究为超快太赫兹量子级联激光器的发展奠定了重要理论和实验基础。