Thin-film lithium-niobate electro-optic platform for spectrally tailored dual-comb spectroscopy.

Laser frequency comb generators on photonic chips open up the exciting prospect of integrated dual-comb microspectrometers. Amongst all nanophotonic platforms, the technology of low-loss thin-film lithium-niobate-on-insulator shows distinguishing features, such as the possibility to combine various optoelectronic and nonlinear optical functionalities that harness second- and third-order nonlinearities, and thus promises the fabrication of a fully on-chip instrument. Here, a critical step towards such achievement is demonstrated with an electro-optic microring-based dual-comb interferometer. Spectra centered at 191.5 THz and spanning 1.6 THz (53 cm−1) at a resolution of 10 GHz (0.33 cm−1) are obtained in a single measurement without requiring frequency scanning or moving parts. The frequency agility of the system enables spectrally-tailored multiplexed sensing, which allows for interrogation of non-adjacent spectral regions, here separated by 6.6 THz (220 cm−1), without compromising the signal-to-noise ratio. Our studies show that electro-optic-based nanophotonic technology holds much promise for new strategies of molecular sensing over broad spectral bandwidths. Thin-film lithium niobate is a promising photonic platform owing to its strong optical nonlinearity and low losses. Here, the utility of this platform is demonstrated as a tunable dual frequency comb spectrometer based on second-order nonlinearities in a proof-of-principle experiment. [ABSTRACT FROM AUTHOR]