We report the extension of broadband degenerate OPO operation further into mid-infrared. A femtosecond thulium fiber laser with output centered at 2050 nm synchronously pumps a 500-μm-long crystal of orientation patterned GaAs providing broadband gain centered at 4.1 µm. We observe a pump threshold of 17 mW and output bandwidth extending from 2.6 to 6.1 µm at the -30 dB level. Average output power was 37 mW. Appropriate resonator group dispersion is a key factor for achieving degenerate operation with instantaneously broad bandwidth. The output spectrum is very sensitive to absorption and dispersion introduced by molecular species inside the OPO cavity.

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We present a novel all-fiber pumped OPCPA architecture to generate self-CEP stable, sub-8 optical cycle duration pulses at 7-micron wavelength approaching millijoulelevel pulse energy at 100 Hz repetition rate. The system yields a peak power of 1.1 GW and, if focused to the diffraction limit, would reach a peak intensity of 7x10 14 W/cm 2. The OPCPA is pumped by a 2-micron Ho:YLF chirped pulse amplifier to leverage the highly efficient and broadband response of the nonlinear crystal ZGP. The 7-micron seed at 100 MHz is generated via DFG from an Er:Tm:Ho multi-arm fiber frequency comb and a fraction of its output optically injects the Ho:YLF amplifier. While the pulse bandwidth at 7 micron is perfectly suited for nonlinear and spectroscopic applications, current parameters offer, for the first time, the possibility to explore strong field physics in an entirely new wavelength range with a ponderomotive force 77 times larger than from an 800 nm source. The overall OPCPA system is very compact and provides a new tool for investigations directly in the molecular finger print region of the electromagnetic spectrum or to drive high harmonic generation to produce fully coherent X-rays in the multi-keV range and possibly zeptosecond temporal waveforms.

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Probing matter with light in the mid-infrared provides unique insight into molecular composition, structure, and function with high sensitivity. However, laser spectroscopy in this spectral region lacks the broadband or tunable light sources and efficient detectors available in the visible or near-infrared. We overcome these challenges with an approach that unites a compact source of phase-stable, single-cycle, mid-infrared pulses with room temperature electric field–resolved detection at video rates. The ultrashort pulses correspond to laser frequency combs that span 3 to 27 μm (370 to 3333 cm−1), and are measured with dynamic range of >106 and spectral resolution as high as 0.003 cm−1. We highlight the brightness and coherence of our apparatus with gas-, liquid-, and solid-phase spectroscopy that extends over spectral bandwidths comparable to thermal or infrared synchrotron sources. This unique combination enables powerful avenues for rapid detection of biological, chemical, and physical properties of matter with molecular specificity.