Observation of Long Turn-On Delay in Pulsed Quantum Cascade Lasers

QCL dynamics: thermal effects and rate equations beyond mean-field approach

“…Obviously the longer the pumping rise time is, the higher threshold current will be technically detected. Thus we observe to the dynamical threshold variation and come to a problem of correct threshold de- This correlates with the experimental data shown in [12] and can be explained by the thermal processes distorting delicate balance between probabilities of non-radiative relaxation and stimulated emission. Build-up time estimations: Here we discuss the selfheating impact on the build-up time, which is important parameter for such applications as LIDAR systems and telecommunication technologies.…”

“…Thus the theoretical predictions show the build-up times of the order of hundred picoseconds at the double threshold, which is the standard operational regime. The recent experiment [12] showed that the real value of the build-up time can reach the order of ten nanoseconds which completely contradicts the provided numerical estimations. In this work we want to investigate this discrepancy thoroughly by means of coupled rate equations.…”

“…Obviously this is due to the heat produced before beginning of generation, that warms a sample reducing the probability of stimulated emission compared to the non-radiative processes. Experimentally this is realized when the pumping is different from the step-like function and shows the finite rise time as done in [12] and shown in Fig. 3.…”

“…The rate equations approximation is well-known and widely used [8,12,13] mathematical approach allowing to describe system with classical or semi-classical behaviour.…”

“…At the same time this simplicity leads to some serious drawbacks. The first one was discussed in [12], where the same system was…”