Enhancing the performance of saturable absorbers through excellence in parameter extraction

Individual fitting methods traditionally struggle to accurately and uniquely extract the parameters of saturable absorbers (SAs), leading to inconsistencies. To overcome this, we introduce a novel simultaneous fitting method, unprecedented in optics to the best of our knowledge, along with what we believe is a new set of fitting functions derived from a two-level system band structure model. These functions enable the simultaneous reproduction of experimental data for both reflectance R(F_out) or transmissivity T(F_out) versus the fluence reflected by the sample F_out and reflectance R(F_in) or transmissivity T(F_in) versus incident fluence F_in, ensuring parameter consistency across diverse characterization techniques. We successfully apply this method to characterize three distinct 1064 SESAM samples using an open-aperture Z-scan device, obtaining consistent parameter results. Furthermore, by generating a mode-locking laser with 1064 SESAM-sample3, we independently evaluate the saturation fluence parameter under mode-locking threshold conditions. The findings provide substantial evidence that our method extracts parameters with higher accuracy. This approach promises to enhance the accuracy and reliability of SA parameter extraction, advancing the field of ultrafast photonics.