Consistent characterization of semiconductor saturable absorber mirrors with singe-pulse and pump-probe spectroscopy

We study the comparability of the two most important measurement methods used for the characterization of semiconductor saturable absorber mirrors (SESAMs). For both methods, single-pulse spectroscopy (SPS) and pump-probe spectroscopy (PPS), we analyze in detail the time-dependent saturation dynamics inside a SESAM. Based on this analysis, we find that fluence-dependent PPS at complete spatial overlap and zero time delay is equivalent to SPS. We confirm our findings experimentally by comparing data from SPS and PPS of two samples. We show how to interpret this data consistently and we give explanations for possible deviations

Characterization of InGaAs and InGaAsN semiconductor saturable absorber mirrors for high-power mode-locked thin-disk lasers

We report a comparative study of carrier dynamics in semiconductor saturable absorber mirrors (SESAMs) containing InGaAs quantum wells and InGaAsN quantum wells (QWs). The static and dynamic reflectivity spectra were measured with a Fourier-transform-infrared-spectrometer and a pump-probe setup, respectively. The influence of rapid thermal annealing (RTA) on carrier dynamics was studied. Due to the reduction of defect states by RTA we observed an increase of the static reflectivity and an increase of the electron–hole recombination time. We demonstrate that nitrogen incorporation causes a decrease of the static reflectivity of the SESAMs, an increase of the modulation depth, and a reduction of the carriers’ recombination time. We also investigated the mode-locking behavior of the SESAMs in an Yb:YAG thin-disk laser oscillator. The highest pulse energies directly obtained from a laser oscillator under stable operation conditions were achieved when using a SESAM with InGaAsN quantum wells