Mid-infrared dual comb spectroscopy via continuous-wave optical parametric oscillation
Dual-comb spectroscopy has demonstrated remarkable capabilities for rapid and sensitive measurements; however, significant challenges still exist in generating high-power, mutually coherent mid-infrared combs. Here we demonstrate that a pair of near-infrared femtosecond frequency combs can be spectrally translated via a continuous-wave optical parametric oscillator. The pair of spectrally translated combs demonstrated high mutual coherence, power per comb tooth in excess of hundreds of microwatts, and were tunable between 4 um and 5 um. Unlike previous approaches which relied upon synchronous optical parametric oscillation, the present approach avoids challenges associated with comb stabilization, low power per comb tooth, and complex cavity designs. Further it is readily amenable to high repetition rates (gigahertz-level and beyond). The flexible and facile nature of this approach provides a robust path for the spectral translation of mode-locked combs, achieving spectral bandwidths limited only by the phase matching bandwidth of the optical parametric oscillator. This approach holds significant promise for applications in chemical kinetics, remote sensing, combustion science, and precision spectroscopy, where the combination of high powers, broad bandwidths, and high measurement rates are transformative.