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Mid-Infrared Frequency Comb Generation and Spectroscopy with Few-Cycle Pulses and χ ( 2 ) Nonlinear Optics

2020; American Physical Society; Volume: 124; Issue: 13 Linguagem: Inglês

10.1103/physrevlett.124.133904

1092-0145

Alexander J. Lind, Abijith S. Kowligy, Henry Timmers, Flávio C. Cruz, Nima Nader, Myles Silfies, Thomas K. Allison, Scott A. Diddams,

Spectroscopy and Laser Applications

Mid-infrared laser frequency combs are compelling sources for precise and sensitive metrology with applications in molecular spectroscopy and spectro-imaging. The infrared atmospheric window between 3-5.5 $\mu$m in particular provides vital information regarding molecular composition. Using a robust, fiber-optic source of few-cycle pulses in the near-infrared, we experimentally demonstrate ultra-broad bandwidth nonlinear phenomena including harmonic and difference frequency generation in a single pass through periodically poled lithium niobate (PPLN). These $\chi^{(2)}$ nonlinear optical processes result in the generation of frequency combs across the mid-infrared atmospheric window which we employ for dual-comb spectroscopy of acetone and carbonyl sulfide with resolution as high as 0.003 cm$^{-1}$. Moreover, cascaded $\chi^{(2)}$ nonlinearities in the same PPLN directly provide the carrier-envelope offset frequency of the near-infrared driving pulse train in a compact geometry.