Sensitive and accurate interferometric pulse characterization via two-photon absorption in Fabry-Pérot laser diodes

Semiconductor lasers offer bifunctionality that enables coherent light generation and linear photodetection from the same device. Additionally, they often operate as efficient Two-Photon Absorption (TPA) detectors due to the significant third-order nonlinearity of their active-region heterostructures. This robust room-temperature TPA response makes them invaluable for applications in ultrafast optics, including the interferometric characterization of femtosecond pulses. Despite extensive studies on the TPA response of commercial photodiodes and custom semiconductor microcavities, semiconductor lasers' potential for accurately characterizing femtosecond pulse durations has not been systematically explored. To address this niche, we use AlGaAs and InGaAsP laser diodes, designed for emission wavelengths of 0.95 μm and 1.3 μm to measure femtosecond pulse at a central wavelength of 1.5 µm. Pulses with durations ranging from sub-50 fs to 150 fs were characterized. The obtained autocorrelation traces were benchmarked against measurements from a conventional Second-Harmonic Generation (SHG) crystal-based autocorrelator. The results demonstrate the capability of Fabry-Pérot (FP) laser structures to perform accurate interferometric autocorrelation measurements. This work underscores the feasibility of semiconductor lasers as versatile and reliable tools for ultrafast pulse diagnostics. It also highlights their potential for wider adoption in nonlinear optics and ultrafast metrology.