实验上观察到自混合干涉信号的幅度仅仅为静态光强的百分之几。反馈光会引起激光二极管阈值电流减小,静态输出光强变化几倍,使激光二极管工作在实际的阈值电流之上。按三镜法布里-珀罗腔结构模型计算激光二极管的出射光强,由干涉函数主极大条件得出光频与反馈光的关系。计算出的自混合干涉信号的波形,以及自混合干涉信号的幅度与静态光强的比值均同实验测量结果一致。在τrC/τi=22.8的情况下, 复合谐振腔可同时有15个谐振模式,这些模随外腔长度的变化小于2.6×10-2 cm-1,远小于法布里-珀罗谐振腔谐振模的线宽3.1 cm-1,光频在内腔谐振模的线宽以内变化。

Ratio of self-mixing interference amplitude and static light intensity from a laser diode is only a few percent based on experimental observation. Feedback light decreases threshold current of laser diode and increases the static light intensity. The feedback light makes laser diode operate over the actual threshold current. The output intensity of laser diode is calculated with a three-mirror Fabry-Pérot cavity system. An equation between light frequency and feedback light is found from the main maximum condition of interference function. Signal waveform of self-mixing interference and ratio of the signal amplitude with the static light intensity are calculated, and the results are coincident with that measured experimentally. There are 15 resonance modes of complex cavity in the case of τrC/τi=22.8 at the same time. The variations of these resonance modes with external cavity length are less than 2.6×10-2 cm-1 and far less than 3.1 cm-1resonance mode width of Fabry-Pérot cavity. The variation of the light frequency is within the resonance mode width of inherent cavity.