Research On Vibration Measurement Based On Self-mixing Interference Effect In Semiconductor Laser

The problem of self-mixing interference stems from the optical feedback effect, gradually people began to make use of it actively to measure all kinds of physical quantities, and this a new measuring technique appears. Self-mixing interference in semiconductor laser is the effect that a portion of the output light of laser diode is reflected or scattered by a moving target. The reflected lights carries the state information of the external target, then mixes with the light inside the cavity, causing a modulation of the laser output power. Because this effect shows a resemblance to two team interference, it is called self-mixing interference. In recent years, with the development of semiconductor laser technique, making use of self-mixing interference in laser diode actively to measure some physical quantities has become the most potential measurement technique.This thesis reviewed the development history of self-mixing interference. The study purport and applying foreground of self-mixing interference were analyzed. The basic theory model of self-mixing effects which is based on the Lang and Kobayashi equations and the three-mirror cavity approach respectively is described, then the properties of self-mixing interference effect are mathematically analyzed. The influences of system factors and the reason of fringe's inclination on the self-mixing interference signal were discussed.The general self-mixing interference system was set up. The self-mixing interference effects were observed in experiments. Then the output signal's properties modulated by sine wave, triangular wave and square wave were discussed. The correctness and the reliability were confirmed by reappearing the phenomena of self-mixing interference reported previously.Finally, this thesis proposes a method of vibration measurement based on self-mixing interference effect. The vibration amplitude and velocity were measured. We modified the general self-mixing interference system. Examined by the experiments, the measurement and accuracy are improved greatly.