Experimental generation of a flat-top beam profile in a stable ring cavity

TL;DR

This paper demonstrates a method to generate a stable, flat-top laser beam profile inside a ring cavity by combining two transverse modes, enabling uniform illumination for atomic trapping without complex phase control.

Contribution

It introduces a novel technique for creating a flat-top beam profile in a stable ring cavity using mode interference, eliminating the need for interferometric phase control.

Findings

Achieved a spatially homogeneous flat-top beam profile.

Successfully covered atomic traps with a large waist beam.

Ensured stability through mechanical, thermal isolation, and laser locking.

Abstract

We create a spatially homogeneous field inside of a ring cavity by combining two transverse modes generated by a single laser through modulation. The interference term between the two modes averages out because of the frequency difference between them, eliminating the need for interferometric control of their relative phase. The use of a ring cavity allows for a large waist for the flat-top profile, big enough to cover the atoms in an atomic trap. The cavity is mechanically and thermally isolated, and the laser light is locked to the cavity using the Pound-Drever-Hall technique. The flat-top profile technique reported here fulfill the vanishing curvature criterion at the center of the profile.