A Compact Dual-Beam Zeeman Slower for High-Flux Cold Atoms

TL;DR

This work tackles the challenge of producing high-flux cold atoms in a compact setup without contaminating optical windows. It introduces a dual-oblique-beam Zeeman slower combined with a capillary-array collimation system to reduce residual atomic flux while preserving deceleration efficiency. Monte Carlo simulations and experiments with $^{87}$Rb and $^{174}$Yb show dramatic improvements in 2D-MOT loading—up to $1.2\times10^9$ atoms/s for Rb and $8.0\times10^{10}$ atoms/s for Yb—along with near-elimination of harmful flux, enabling a compact slower of length about $44$ cm. These results point to a robust, scalable platform for high-flux, multi-species cold-atom applications in metrology, quantum computation, and simulation.

Abstract

We present a compact design of dual-beam Zeeman slower optimized for efficient production of cold atom applications. Traditional single-beam configurations face challenges from substantial residual atomic flux impacting downstream optical windows, resulting in increased system size, atomic deposition contamination, and a reduced operational lifetime. Our approach employs two oblique laser beams and a capillary-array collimation system to address these challenges while maintaining efficient deceleration. For rubidium ($^{87}$Rb), simulations demonstrate a significant increase in the fraction of atoms captured by a two-dimensional magneto-optical trap (2D-MOT) and nearly eliminate atom-induced contamination probability at optical windows, all within a compact Zeeman slower length of 44 cm. Experimental validation with Rb and Yb demonstrates highly efficient atomic loading within the same compact design. This advancement represents a substantial improvement for high-flux cold atom applications, providing reliable performance for high-precision metrology, quantum computation and simulation.

Figures (7)

• Figure 1: Schematic of the dual-beam small-angle Zeeman slower and capillary array. The atomic beam is effusively emitted from an oven and collimated through a capillary array before entering the Zeeman slower region. The parameter $L$ is the length of the deceleration region, $L{'}$ the length of the Zeeman deceleration light path, and $\theta_L$ the angle between the Zeeman slower beam and the central axis. The blue spot is the center of 2D-MOT, which is positioned immediately after the deceleration region of the Zeeman slower for simplicity.
• Figure 2: Maximum achievable deceleration velocity of rubidium atoms with different beam angles in the double-beam Zeeman slower. The solid red line, dark blue dotted line, and light blue dotted line correspond to $L=11,28,70$ cm respectively.
• Figure 3: (a) Magnetic field distribution along the Zeeman slower axis for different laser angles $\theta_L$. The deviation from the zero-degree condition is marginal at small angles ($\theta_L \leq 5^\circ$), ensuring effective deceleration. (b) Doppler deceleration profiles showing reduced efficiency in larger $\theta_L$, with only the central region maintaining optimal acceleration.
• Figure 4: Ratio of harmful atomic flux ($\Phi_{\text{harm}}/\Phi_{\text{tol}}$) as a function of beam angle $\theta_L$ for different $L^{'}$ values. $L$ is set to $70$ cm. (a) The three curves represent $L^{'}=40$ cm, $50$ cm, and $60$ cm from right to left. (b) For each angle $\theta_L$, ratio of harmful atomic flux ($\Phi_{\text{harm}}/\Phi_{\text{tol}}$) is shown as a function of $L^{'}$.
• Figure 5: Histogram showing the velocity distribution of atoms after deceleration, with a peak at $12.5\pm0.5$ m/s. The probability without Zeeman slower (red curve) is scaled by $\times$10 for visibility. (b) Cumulative distribution confirms that about $5.2$% of atoms reach the MOT with velocities between $0-30$ m/s, representing a 235-fold improvement over the atomic beam without Zeeman slower cooling.