Noise and correlation effects in GaAlAs broad-band sources

Intensity fluctuations in GaAlAs superluminescent diodes have been measured at low frequencies (
\sim-1
kHz). A monotonic increase in the relative noise with increasing dc bias current was observed. The correlation in noise for light emitted from the two facets was also investigated. The coherence function for the emission from the two facets was found to be near zero at low current levels, and to increase to a maximum value near 0.7 at higher currents. A model which hypothesizes uncorrelated local current fluctuations in different parts of the active region explains the main features of the measured results.