An efficient method to generate near-ideal hollow beams of different shapes for box potential of quantum gases

TL;DR

This paper introduces a combined optical scheme using fixed optics and a DMD to generate high-quality, shape-variable hollow beams for creating near-ideal box potentials in ultracold quantum gases, enhancing homogeneity and control.

Contribution

The novel approach integrates fixed optics and a DMD to produce efficient, high-quality hollow beams with customizable shapes for quantum gas experiments, surpassing previous methods.

Findings

Achieved potential walls with a power-law exponent over 100.

Improved light efficiency compared to mask or DMD-only shaping.

Enabled creation of highly homogeneous two-dimensional quantum gases.

Abstract

Ultracold quantum gases are usually prepared in conservative traps for quantum simulation experiments. The atomic density inhomogeneity, together with the consequent position-dependent energy and time scales of cold atoms in traditional harmonic traps, makes it difficult to manipulate and detect the sample at a better level. These problems are partially solved by optical box traps of blue-detuned hollow beams. However, generating a high-quality hollow beam with high light efficiency for the box trap is challenging. Here, we present a scheme that combines the fixed optics, including axicons and prisms, to pre-shape a Gaussian beam into a hollow beam, with a digital micromirror device (DMD) to improve the quality of the hollow beam further, providing a nearly ideal optical potential of various shapes for preparing highly homogeneous cold atoms. The highest power-law exponent of potential walls can reach a value over 100, and the light efficiency from a Gaussian to a hollow beam is also improved compared to direct optical shaping by a mask or a DMD. Combined with a one-dimensional optical lattice, a nearly ideal two-dimensional uniform quantum gas with different geometrical boundaries can be prepared for exploring quantum many-body physics to an unprecedented level.