Low-frequency intensity noise in semiconductor lasers

The observed 1/f noise in the light-output power S/sub p/ of four different types of heterostructure lasers is explained in terms of spatially uncorrelated gain fluctuations and spontaneous emission fluctuations. Two possible noise sources are suggested: fluctuations in the absorption coefficient and fluctuations in the number of free carriers. Both models are in agreement with the experimental results obtained from index-guided and gain-guided diodes at wavelengths of 1.3 and 0.8 mu m. The dependence S/sub p/ varies as P/sup m/ has been observed with P the average light-output power and m=3/2 under spontaneous emission, a small transition region with m=5/2, m=4 in the superradiation region, and 0>