Artist's illustration (Brad Baxley, https://www.parttowhole.com/) of the spectral translation of an electro-optic frequency comb using optical parametric oscillation in a chip-integrated microresonator.
In a recent paper in Nature Photonics that is in collaboration with David Long at NIST, we demonstrate a new approach to high-resolution spectroscopy of quantum systems such as alkali atomic vapors. In particular, we show that agile electro-optic frequency combs can be efficiently spectrally translated to a variety of wavelengths in the visible and short near-infrared using Kerr optical parametric oscillation (OPO) in a photonic integrated circuit microresonator. Amongst these wavelengths is 852.3 nm, which is the Cs D2 transition that is utilized in many quantum applications. We use our spectrally-translated electro-optic comb to effectively perform sub-Doppler spectroscopy of this transition in Cs vapor, showcasing that the overall process of generating the electro-optic comb is compatible with its intended applications.
This work makes use of our previous results in developing wavelength-accurate OPO devices that use a single pump laser technology to reach a variety of important wavelengths in quantum science. Here, we show that a single pump laser plus a single electro-optic phase modulator can create frequency combs with up to 1 million teeth across a bandwidth of around gigahertz across any one of a broad range of wavelengths in the visible and short near-infrared.