宽谱太赫兹量子级联激光器的自混合特性

Self-mixing interference in broadband terahertz quantum cascade lasers

基于传输矩阵理论及多模速率方程,研究了宽谱太赫兹量子级联激光器在不同光反馈强度下的自混合动力学特性。研究发现,在弱反馈下光场自混合对激光器光谱特性影响很小;反射物位置移动时的自混合信号呈正弦规律变化,同时自混合信号幅度随反射物位置的变化表现出周期性调制现象。宽谱量子级联激光器在弱反馈下可以应用于测距、成像及光谱测量。在强反馈下,宽谱激光器光谱受自混合影响显著,并有新的模式在原自由运行模式附近出现;但随着反射物移动,自混合信号波峰个数同弱反馈条件下一致,可正确描述反射物的移动规律。因此,强反馈下宽谱量子级联激光器仍可在一定条件下实现微米级的测距和成像技术。这一研究将有助于发展基于宽谱太赫兹量子级联激光器自混合现象的传感器应用。

Self-mixing interference in broadband terahertz(THz)Quantum Cascade Lasers(QCLs)are studied by the transition matrix theory and rate equations method.Under weak optical feedback strength,with the target moving in uniform motion,the self-mixing signal changes in a sine-like waveform.It is found that the self-mixing signal of the broadband THz QCLs under weak feedback can be applied to range finding,imaging,and spectral measurement.Under strong optical feedback,the spectrum is affected by the optical feedback obviously,while new modes arise near the solitary modes.As a target moves in uniform motion,the self-mixing signal shows the same number of peaks as that in weak feedback case.Therefore,the broadband QCLs under strong feedback cannot be applied to spectral measurement,but it can be applied to realize micron-magnitude range finding and imaging under certain conditions.The study is helpful to the application of THz sensor technology based on self-mixing interference in broadband THz QCLs.