Mode Switching in Injection Lasers Induced by Temperature Variation and Optical Feedback

Effects of optical feedback and temperature fluctuation on the longitudinal mode behavior of an AlGaAs injection laser have been studied utilizing the transient temperature variation produced by pulsed current excitation. Small temperature fluctuations (∼0.01 K for a feedback distance of about 300 mm) induce mode switching at relatively low power levels (1∼4 mW). This behavior is shown to be consistent with the compound cavity model and the gain suppression effect associated with the inhomogeneity of the gain spectrum. It has also been found that mode switching is always accompanied by a change in the output power, indicating that this phenomenon is an important source of excess optical noise.