Nonlinear Dynamics in Semiconductor Lasers - Abstract
Klehr, Andreas
Detailed experimental and theoretical investigations of the dynamics of internally wavelength stabilized broad area distributed Bragg reflector InGaAs single quantum well (SQW) lasers with emission wavelengths of about 905 nm are presented. For high peak current, small pulse width, high repetition rate, and high power efficiency new electrical pulse drivers with final stages based on GaN transistors are developed. Nearly rectangular current pulses with widths between 4 ns and 20 ns and amplitudes up to 150 A are generated. Pulse powers of 32 W with optical pulse widths between 2 ns and 10 ns are achieved. The temporal evolution of the lateral near field profiles and optical spectra is investigated with a streak camera. The lasers turn on at different lateral positions at different times, depending on the amplitudes of the current pulses and varying from device to device. Small changes in the index and gain profiles can favor the laser turn on of different lateral modes. After a few nanoseconds down to hundreds of picoseconds, depending on the injection current, the lasers reach a quasi-stationary regime. Temporally and spatially resolved spectral measurements at high current pulse excitation show a strong variation of the intensity and spectral behavior of different lateral modes at different times during the optical pulse. The experiments are compared with simulation results of the spatio-temporal behavior using a model based on paraxial wave equation for the optical field coupled to a time-dependent diffusion equation for the excess carriers. The simulation results show, as in the experiment, strong intensity fluctuations.