Noise Properties of Semiconductor Lasers in Simulated Conditions of Optical Playback

As semiconductor lasers are being used in more advanced optical systems, the noise properties of the light output are of increasing importance. We present an experimental analysis of noise due to feedback into index guided lasers. Our measurement set-up reproduces that in which the laser may be used for reading information from a mechanically unstable reflecting surface, as for example an optical disk. The analysis includes the dependence of noise on output power level, proportion of the reflected light returned to the laser, external cavity length and modulation level. Finally, the noise performance of different lasers, with and without modulation, is compared in a simple analysis of the requirements of optical disk systems.