Sub-Doppler laser cooling of ${}^{39}$K via the 4S$\to$5P transition

Abstract

We demonstrate sub-Doppler laser cooling of ${}^{39}$K using degenerate Raman sideband cooling via the 4S${}_{1/2}\to$5P${}_{1/2}$ transition at 404.8 nm. By using an optical lattice in combination with a magnetic field and optical pumping beams, we obtain a spin-polarized sample of up to $5.6\times 10^7$ atoms cooled down to a sub-Doppler temperature of 4 $\mu$K, reaching a peak density of $3.9\times 10^9$ atoms/cm${}^3$, a phase-space density greater than $10^{-5}$, and an average vibrational level of $⟨\nu ⟩=0.6$ in the lattice. This work opens up the possibility of implementing a single-site imaging scheme in a far-detuned optical lattice utilizing shorter wavelength transitions in alkali atoms, thus allowing improved spatial resolution.

Submission to SciPost