A high numerical aperture (NA = 0.92) objective lens for imaging and addressing of cold atoms

TL;DR

This paper presents the design, construction, and characterization of a high-NA objective lens suitable for cold atom experiments, enabling advanced quantum control with high spatial resolution and efficiency.

Contribution

It introduces a novel high-NA (0.92) objective lens compatible with ultra-high vacuum environments, featuring a long working distance and insensitivity to mechanical tolerances.

Findings

Achieved a NA of 0.92 with a 150 μm working distance.

Demonstrated wavefront aberration measurement using a tapered optical fiber.

Enabled potential applications in quantum control and photon collection.

Abstract

We have designed, built, and characterized a high-resolution objective lens that is compatible with an ultra-high vacuum environment. The lens system exploits the principle of the Weierstrass-sphere solid immersion lens to reach a numerical aperture (NA) of 0.92. Tailored to the requirements of optical lattice experiments, the objective lens features a relatively long working distance of 150 micrometers. Our two-lens design is remarkably insensitive to mechanical tolerances in spite of the large NA. Additionally, we demonstrate the application of a tapered optical fiber tip, as used in scanning near-field optical microscopy, to measure the point spread function of a high NA optical system. From the point spread function, we infer the wavefront aberration for the entire field of view of about 75 micrometers. Pushing the NA of an optical system to its ultimate limit enables novel applications in quantum technologies such as quantum control of atoms in optical microtraps with an unprecedented spatial resolution and photon collection efficiency.