Noise characteristics of stripe-geometry double-heterostructure junction lasers operating continuously - I. Intensity noise at room temperature

Measurements of the noise fluctuations present in the output intensity from stripe-geometry double-heterostructure junction lasers operating continuously at room temperature are reported. In some but not all the lasers studied, the low-frequency (50-MHz) fluctuations exhibit the quieting expected of an amplitude-stabilized oscillator operating above threshold. The intensity noise in these lasers becomes shot noise limited at currents about 10 percent above threshold, even when many longitudinal modes are oscillating. Additional measurements demonstrate explicitly the effective elimination of the wave-interaction, or excess, noise during the transit of the threshold region. However, in other lasers which are nominally similar, only a partial reduction of the excess noise occurs above threshold, resulting in a noise level which can be more than ten times the shot-noise limit. In addition, we find in all lasers studied thus far no quieting at high frequencies (4 GHz), in apparent contradiction to the behavior expected of a well-stabilized oscillator.