Phase-space properties of magneto-optical traps utilising micro-fabricated gratings

TL;DR

This paper investigates the phase-space properties of micro-fabricated grating-based magneto-optical traps, demonstrating enhanced atom collection efficiency and achieving large atom numbers with sub-Doppler temperatures through theoretical and experimental analysis.

Contribution

It provides a detailed theoretical and experimental study of on-chip MOT temperature and density across different chip geometries, highlighting the benefits of micro-fabricated gratings.

Findings

Increased atom number (2x10^7) with optimized chips.

Achieved sub-Doppler temperatures (50 μK) after optical molasses.

Enhanced collection efficiency due to larger capture volume.

Abstract

We have used diffraction gratings to simplify the fabrication, and dramatically increase the atomic collection efficiency, of magneto-optical traps using micro-fabricated optics. The atom number enhancement was mainly due to the increased beam capture volume, afforded by the large area (4cm^2) shallow etch (200nm) binary grating chips. Here we provide a detailed theoretical and experimental investigation of the on-chip magneto-optical trap temperature and density in four different chip geometries using 87Rb, whilst studying effects due to MOT radiation pressure imbalance. With optimal initial MOTs on two of the chips we obtain both large atom number (2x10^7) _and_ sub-Doppler temperatures (50uK) after optical molasses.