Robust and Compact Ultrafast mid-IR Laser Technology for Driving Secondary Sources

This project addresses the needs outlined in Section 31 (e) of the Topics for FY 2022 Phase I, Release 2 DoE SBIR/STTR. Laser systems have been developed, that successfully produce ultrashort pulses at 0.8 µm, 1 µm, 1.5 µm and 2 µm wavelength either in solid-state or fiber laser architectures. Delivering ultrashort pulses in the mid-IR spectral region (l >3 µm) has however so far been possible via frequency down-conversion schemes that are typically bulky, lossy, and environment sensitive. There is however a great need for sources of stable, compact and turn-key ultrashort pulses in the mid-IR for a wide variety of applications ranging from spectroscopy of gases for industrial environment monitoring, spectroscopy of the next generation of quantum information materials, or to drive secondary sources such as e-beams relying on dielectric laser accelerators (DLA) or coherent soft X-rays based on high harmonic generation (HHG). In phase I of this project we will demonstrate a stable mid-IR platform that will deliver femtosecond pulses at 100 MHz repetition rate, sub-nJ to nJ energy at both 3 µm and 2 µm wavelength. Owing to the time and budget limitations of Phase I, the 3 µm pulses will be generated in a combined fiber/free space setting that will be used to design an all-fiber architecture. In phase II, the designed all-fiber approach will be implemented and the pulses at 2 µm and 3 µm wavelength will be scaled to the mJ energy level at kHz repetition rate. The system developed in phase I would find applications in mid-IR spectroscopy providing access – from a single box – to two long-wavelength spectral bands in a turn-key and robust architecture that can further be turned into a frequency comb. In addition, with limited further development, the energy of the 2 µm wave could be scaled and allow parametric amplification of the 3 µm wave, thereby producing an ultrabroadband 6 µm wave, precisely in the spectral range of rovibrational absorption band for a wide range of molecules. Further, the system delivered in Phase I would also make an ideal seed laser for 3 µm OPCPAs, an ideal driver for a secondary source of coherent soft x-ray radiation (200-1200 eV photon energy). Such secondary source would in turn allow spectroscopy on technologically relevant magnetic material and alloys with absorption in the 600-900 eV range, diffractive imaging with sub-5 nm resolution, a resolution range of high importance for the inspection of photolithography masks, or seed FELs..