Offset-Free Gigahertz Midinfrared Frequency Comb Based on Optical Parametric Amplification in a Periodically Poled Lithium Niobate Waveguide

Compact laser frequency combs covering the midinfrared ``fingerprint'' spectral region are desirable light sources for high-sensitivity, high-resolution detection of target molecules. The authors leverage the nonlinear properties of chip-scale Si${}_{3}$N${}_{4}$ and periodically poled LiNbO${}_{3}$ waveguides to obtain a tunable, energy-efficient mid-IR frequency comb. Here the pulse energy needed for a given power per comb line is nearly two orders of magnitude lower than for conventional systems. These results are promising for applications in environmental, medical, and industrial diagnostics.