Sub-Doppler spectroscopy of quantum systems through nanophotonic spectral translation of electro-optic light

TL;DR

This paper introduces a nanophotonic spectral translation technique using electro-optic combs and third-order nonlinearities in silicon nitride, enabling high-resolution, tunable spectroscopy of quantum systems like cesium vapor.

Contribution

It demonstrates a novel, efficient method for sub-Doppler spectroscopy through spectral translation with electro-optic combs and integrated nanophotonics, enhancing quantum sensing capabilities.

Findings

Achieved sub-Doppler spectroscopy of cesium hyperfine transitions.

Enabled wide tunability of signal and idler frequencies via dispersion engineering.

Demonstrated high coherence and efficiency in spectral translation.

Abstract

An outstanding challenge for deployable quantum technologies is the availability of high-resolution laser spectroscopy at the specific wavelengths of ultranarrow transitions in atomic and solid-state quantum systems. Here, we demonstrate a powerful spectroscopic tool that synergistically combines high resolution with flexible wavelength access, by showing that nonlinear nanophotonics can be readily pumped with electro-optic frequency combs to enable highly coherent spectral translation with essentially no efficiency loss. Third-order (\c{hi}(3)) optical parametric oscillation in a silicon nitride microring enables nearly a million optical frequency comb pump teeth to be translated onto signal and idler beams; while the comb tooth spacing and bandwidth are adjustable through electro-optic control, the signal and idler carrier frequencies are widely tuneable through dispersion engineering. We then demonstrate the application of these devices to quantum systems, by performing sub-Doppler spectroscopy of the hyperfine transitions of a Cs atomic vapor with our electro-optically-driven Kerr nonlinear light source. The generality, robustness, and agility of this approach as well as its compatibility with photonic integration are expected to lead to its widespread applications in areas such as quantum sensing, telecommunications, and atomic clocks.