Spatial shaping for generating arbitrary optical dipoles traps for ultracold degenerate gases

TL;DR

This paper introduces two spatial-shaping methods—phase and amplitude—for creating customizable two-dimensional optical dipole traps to confine ultracold atoms, enabling flexible potential networks for quantum gas experiments.

Contribution

It presents novel phase-contrast and amplitude-based techniques for generating arbitrary optical dipole traps, demonstrated on thermal atoms and Bose-Einstein condensates.

Findings

Phase-contrast method effectively creates complex potential patterns.

Amplitude masks can trap degenerate gases despite higher losses.

Both methods enable flexible, reconfigurable optical trapping geometries.

Abstract

We present two spatial-shaping approaches -- phase and amplitude -- for creating two-dimensional optical dipole potentials for ultracold neutral atoms. When combined with an attractive or repulsive Gaussian sheet formed by an astigmatically focused beam, atoms are trapped in three dimensions resulting in planar confinement with an arbitrary network of potentials -- a free-space atom chip. The first approach utilizes an adaptation of the generalized phase-contrast technique to convert a phase structure embedded in a beam after traversing a phase mask, to an identical intensity profile in the image plane. Phase masks, and a requisite phase-contrast filter, can be chemically etched into optical material (e.g., fused silica) or implemented with spatial light modulators; etching provides the highest quality while spatial light modulators enable prototyping and realtime structure modification. This approach was demonstrated on an ensemble of thermal atoms. Amplitude shaping is possible when the potential structure is made as an opaque mask in the path of a dipole trap beam, followed by imaging the shadow onto the plane of the atoms. While much more lossy, this very simple and inexpensive approach can produce dipole potentials suitable for containing degenerate gases. High-quality amplitude masks can be produced with standard photolithography techniques. Amplitude shaping was demonstrated on a Bose-Einsten condensate.