Optical feedback-induced noise in laser diodes in optical-disc systems

We analyze intensity and frequency noises induced in laser diodes due to optical feedback phenomenon in optical disk systems. The analysis is based on numerical integration of time-delay rate equations of the photon number, optical phase and injected electron number. Light versus current characteristics under different strengths of optical feedback are simulated. Bifurcation analysis is employed to examine influence of optical feedback on laser dynamics. The corresponding influence on both spectral profiles and low-frequency parts of intensity and frequency noises are presented. We discuss also influences of injection current, distance of the disc-to-laser, and optical feedback-induced phase change of laser light on noise properties. Noises are enhanced when chaos is induced, while they attain minimum levels under continuous wave operation just before the laser starts routes-to chaos. Noise characteristics are found to be sensitive to optical feedback-induced phase change.