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在自混合干涉中激光频率受外腔反馈和外腔反射面运动的影响。由内外复合腔模型给出激光二极管(LD)谐振腔前后端面出射的光场,外腔反馈和外腔运动引起的激光频移,以及自混合干涉信号的频率。实验观察外腔反馈引起的激光频移和自混合干涉信号的频谱。激光的频移包括谐振频移和运动频移,在外腔反射面运动频率较低时,谐振腔前后端面出射光的频移近似相同为谐振频移。外腔反射面高频运动时,谐振腔前后端面出射光的频移不相同,前端面出射光频移会由运动频移决定。外腔反馈极弱时,自混合干涉信号的频率与反射光多普勒频移相同,外腔反馈增强,随外腔反射面振动自混合干涉信号的频率存在尖锐振荡,其最大频率超过反射光多普勒频移的1.6倍。
In self-mixing interference, the laser frequency is affected by external feedback and external reflection. The light field exiting the anterior and posterior faces of the laser diode (LD) cavity, the laser frequency shift caused by the external cavity feedback and the external cavity motion, and the frequency of the self-mixing interference signal are given by the internal and external cavity models. The frequency shift of the laser induced by external cavity feedback and the spectrum of the self-mixing interference signal were observed experimentally. The frequency shift of the laser includes the resonance frequency shift and the movement frequency shift. When the movement frequency of the external cavity reflection surface is low, the frequency shift of the exit light at the front and back end faces of the resonator is approximately the same as the resonance frequency shift. When the external reflection surface is in high-frequency movement, the frequency shift of the outgoing light at the front and back ends of the resonant cavity is not the same, and the frequency shift of the outgoing light at the front end surface is determined by the frequency shift of movement. When the external cavity feedback is very weak, the self-mixing interference signal has the same frequency as the Doppler shift of the reflected light. The feedback of the external cavity is enhanced. The frequency of the self-mixing interference signal oscillates sharply with the vibration of the external cavity reflection surface, and the maximum frequency exceeds the reflected light Doppler frequency shift of 1.6 times.