Self-mixing speckle interference in DFB laser diode

The statistical analysis and experimental results of self-mixing speckle interference in the distributed feedback (DFB) laser are presented in this paper. Dynamics solution of output gain variation in the DFB cavity is deduced on the basis of speckle theory and self-mixing interference in the DFB laser, when external optical feedback comes from a moving rough surface. By numeric simulations and experiments, the dynamic output variations of the DFB laser as well as their probability density functions (PDFs) are analyzed. Both results of simulations and experiments are in agreement with each other. The experimental results show that this speckle signal processing can be used to measure velocity of target.