Purely optical macroscopic trap for alkaline-earth and similar atoms

Abstract

We consider a laser cooling and trapping of alkaline-earth and similar atoms in a bichromatic field resonant to a closed optical transition $^1S_0 \to \, ^1P_1$ or $^1S_0 \to \, ^3P_1$. It is shown that new kinetic effects emerge compared to monochromatic fields, enabling the formation of a deep macroscopic trap capable of capturing and cooling neutral atoms to sub-Doppler temperatures. Such a purely optical macroscopic trap can serve as an alternative to the well-known magneto-optical trap and can be used in applications requiring minimization of the magnetic field in the cold atom cloud region. The obtained results are of interest for the new generation of quantum sensors and optical frequency standards.

Figures (7)

• Figure 1: The scheme of energy levels of ytterbium-171 for laser cooling and trapping in a bichromatic field. Solid arrows represents transitions induced by components of the bichromatic field ${\bf E}_1$ and ${\bf E}_2$.
• Figure 2: Double $lin \perp lin$ bichromatic field configuration.
• Figure 3: Macroscopic optical potential $U(z)$ in units of $\hbar \gamma$ in a bichromatic field. Field detunings $\delta_1 = -346 \gamma$ ($\simeq 10\,$GHz), and $\delta_2 = -3 \gamma$. Intensities of the waves of the frequency components $I_1 \simeq 57$ W/cm$^2$ ($\Omega_{01} \simeq 22 \gamma$), and $I_2 \simeq 0.4$ W/cm$^2$ ($\Omega_{02} \simeq 1.9 \gamma$).
• Figure 4: Force on an atom moving with velocity $v$ in a bichromatic field in the region of the global minimum of the optical potential $z=0$ (black line) and on the slope of the optical potential $z=0.3$ cm (blue line). The field parameters correspond to Fig.\ref{['fig:F3']}.
• Figure 5: The Wigner function of (a) the atomic phase distribution ${\cal F}(z, p)$ and (b) the momentum distribution of cold atoms in the macroscopic potential of the bichromatic field of double $lin \perp lin$ configuration. The field parameters correspond to Fig.\ref{['fig:F3']}.