Heating of a quantum cascade laser under pulsed pumping: theory and experiment

The paper considers the features of the quantum cascade laser operation under pulsed current pumping and corresponding heating. We have shown that, as the steepness of the pump pulse front edge decreases, the threshold current shifts towards higher values by tens of milliamps, which is associated with intense heating of the QCL active region in the first moments after the start of pumping. A model based on the thermodiffusion approximation is proposed to describe the experiment. Studying the time dependence of laser radiation intensity has shown that, within the interval of hundreds of nanoseconds after the pump pulse onset, power transfer to the main heat sink gets activated; thereat, the heat removal efficiency reaches 50–75% of the total power consumption, which significantly reduces the rate of active region heating.