Precise mid-infrared characterization of InGaSb/GaSb SESAMs

There is a strong interest in mid-infrared (mid-IR) Semiconductor Saturable Absorber Mirrors (SESAMs) [1] . We have established an accurate nonlinear reflectivity and time-resolved SESAM characterization which covers a wavelength range from 1.9 µm to 3 µm transferring our near-IR knowhow [2] , [3] to the mid-IR ( Fig. 1a , 1b ). The nonlinear reflectivity of a SESAM is characterized by the saturation fluence, modulation depth, non-saturable losses and a rollover parameter. The temporal response determined with the pump-probe (PP) setup is described by a fast and slow recovery time. We present the nonlinear reflectivity and PP characterization with three different SESAMs designed and grown at ETH Zurich within FIRST clean room facility. The low-finesse antiresonant SESAMs contain either 2, 3 or 4 In 0.26 Ga 0.74 Sb quantum wells (QWs), operating at a wavelength of 2.05 µm (see absorption dip in Fig. 1c ).