Abstract

The maximum bandwidth of a semiconductor laser is limited by the damping of the frequency response. Although the damping value in bulk lasers is independent of structure, the damping value varies by a factor of 40 in different quantum well designs. Several theories have been proposed to explain this phenomenon including spectral hole burning, dynamic carrier heating, and carrier transport. In an effort to discern which mechanism is dominant, we have measured the temperature dependence of the damping effect in quantum well lasers. Relative intensity noise spectra have been measured for strained InGaAs/GaAs single quantum well (SQW) and compressive strained InGaAs/InP multiple quantum well (MQW) lasers in the temperature range from -70 to 50°C. The differential gain, which was estimated from the resonance frequency dependence on the square root of output power, increased exponentially as the temperature is decreased for both GaAs and InP lasers. Measured values of the slope of the damping factor vs the square of resonance frequency plots (K), were between 0.15 ns and 0.25 ns and relatively insensitive to the temperature for the InGaAs/GaAs SQW laser. The InGaAs/InP MQW laser, which had a large K value (1.0 ns) at room temperature (20°C), showed a rapid increase of K value for temperatures above 0°C. Below 0°C, K values were less sensitive to the temperature.

© 1991 Optical Society of America