太赫兹量子级联激光器中的瞬态啁啾动力学
Transient Chirp Dynamics in Terahertz Quantum Cascade Lasers
浏览论文内容
中文总结 AI 辅助
本文通过片上外差方案实验研究单模太赫兹量子级联激光器的瞬态热啁啾动力学，识别三种啁啾特征并建立双节点热模型，相关发现支撑太赫兹频率梳等应用。
中文摘要 AI 辅助
激光频率啁啾是半导体激光器中普遍存在的动力学过程，对调频光子系统至关重要。在中红外（MIR）和太赫兹（THz）波段，量子级联激光器（QCL）是兼具高功率、窄线宽和小型化优势的理想光源。尽管中红外QCL的啁啾动力学已被研究，但太赫兹QCL的瞬态啁啾行为——尤其是微秒到毫秒 timescale 上的热啁啾——仍未得到充分探索。本文通过片上外差方案实验研究单模太赫兹QCL的瞬态热啁啾动力学，采用两个单片集成的单模QCL：一个脉冲QCL作为被测器件，一个连续波（CW）QCL同时作为本振（LO）和超快太赫兹探测器。通过外差下变频将频率啁啾映射到射频（RF）域，通过改变电流和温度，观察到三种 distinct 啁啾特征：单向向下啁啾、V形啁啾和单向向上啁啾。双节点热模型重现了与实验吻合良好的动力学，还识别出多模 regime 中的啁啾动力学，显示出灵敏动态光谱表征的潜力。这些发现加深了对太赫兹QCL热啁啾机制的理解，并为太赫兹频率梳、调频连续波（FMCW）雷达和高速相干通信的应用提供支持。
英文摘要
Laser frequency chirp is a ubiquitous dynamical process in semiconductor lasers, vital for frequency-modulated photonic systems. In the mid-infrared (MIR) and terahertz (THz) ranges, quantum cascade lasers (QCLs) are ideal sources with high power, narrow linewidth and compact size. While chirp dynamics in MIR QCLs have been studied, the transient chirp behavior of THz QCLs--particularly the thermal chirp on microsecond to millisecond timescales--remains largely unexplored. Here, we experimentally investigate transient thermal chirp dynamics in single-mode THz QCLs via an on-chip heterodyne scheme. Twin monolithically integrated single-mode QCLs are used: one pulsed QCL as the device under test, and one continuous-wave (CW) QCL serving as both local oscillator (LO) and ultrafast THz detector. The frequency chirp is mapped to the radio-frequency (RF) domain by heterodyne down-conversion. By varying current and temperature, we observe three distinct chirp features: unidirectional down-chirp, V-shaped chirp, and unidirectional up-chirp. A two-node thermal model reproduces the dynamics with good agreement with experiments. Chirp dynamics in the multi-mode regime are also identified, showing the potential for sensitive dynamic spectral characterization. These findings deepen the understanding of THz QCL thermal chirp mechanisms and support applications in THz frequency combs, frequency-modulated continuous-wave (FMCW) radar, and high-speed coherent communications.
