5-13.5 µm broadband tunable long-wave infrared femtosecond laser

We introduce a broadband tunable femtosecond laser source in the long-wave infrared (LWIR), covering a range of 5-13.5 µm, based on the integration of optical parametric amplification (OPA) and difference frequency generation (DFG) techniques. We utilize a dual-stage tuning method, combined with the high nonlinear coefficient and broadband phase matching range of BaGa4Se7 (BGSe) crystal, to facilitate significant improvements in spectral coverage and energy efficiency. The laser yields a peak output energy of 43 µJ and maintains energies above 10 µJ across the entire tuning range, with an average power output exceeding 10 mW. The pulse duration at the central wavelength of 8.3 µm is measured at 72 fs full width at half-maximum (FWHM) using the electro-optic sampling method. This LWIR femtosecond laser can be used in many applications, such as molecular fingerprint spectral analysis, ultrafast chemical reaction spectral analysis, material science, and ultrafast physics research, providing an important research basis for the generation and application of mid-infrared ultrafast laser sources.