  A high-resolution broad-spectral-bandwidth spectrometer on a chip would
create new opportunities for gas-phase molecular fingerprinting, especially in
environmental sensing. A resolution high enough to observe transitions at
atmospheric pressure and the simultaneous sensitive detection of multiple atoms
or molecules are the key challenges. Here, an electro-optic microring-based
dual-comb interferometer, fabricated on a low-loss lithium-niobate-on-insulator
nanophotonic platform, demonstrates significant progress towards such an
achievement. Spectra 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.
