# Fabrication of Precision Hemispherical Mirrors for Quantum Optics Applications

## TL;DR

This paper reports the fabrication and precise characterization of nearly perfect hemispherical aluminum mirrors with high numerical aperture for quantum optics, achieving nanometer-level form accuracy suitable for advanced optical applications.

## Contribution

It introduces a method for producing ultra-precise hemispherical mirrors with high NA using diamond turning and in-situ interferometry, demonstrating significant improvements in form accuracy.

## Key findings

- RMS form errors below 25 nm achieved
- Mirror with RMS error of 14 nm and PV error of 88 nm
- Form accuracy of λ=50 for visible optics

## Abstract

High precision, high numerical aperture mirrors are desirable for mediating strong atom-light coupling in quantum optics applications and can also serve as important reference surfaces for optical metrology. In this work we demonstrate the fabrication of highly-precise hemispheric mirrors with numerical aperture NA = 0.996. The mirrors were fabricated from aluminum by single-point diamond turning using a stable ultra- precision lathe calibrated with an in-situ white-light interferometer. Our mirrors have a diameter of 25 mm and were characterized using a combination of wide-angle single- shot and small-angle stitched multi-shot interferometry. The measurements show root- mean-square (RMS) form errors consistently below 25 nm. The smoothest of our mirrors has a RMS error of 14 nm and a peak-to-valley (PV) error of 88 nm, which corresponds to a form accuracy of $\lambda$=50 for visible optics.