Tight focusing of plane waves from micro-fabricated spherical mirrors

TL;DR

This paper derives a formula for the light field of plane waves reflected by spherical mirrors, demonstrating sub-wavelength focusing with micro-fabricated mirrors suitable for scalable optical trapping arrays.

Contribution

It provides a new analytical formula applicable to deep spherical mirrors, enabling sub-wavelength focusing in micro-fabricated optical systems.

Findings

Sub-wavelength spot sizes are achievable with micro-fabricated spherical mirrors.

The formula is valid for deep mirrors with large aperture-to-curvature ratios.

Potential for scalable optical trapping arrays without complex optical systems.

Abstract

We derive a formula for the light field of a monochromatic plane wave that is truncated and reflected by a spherical mirror. Our formula is valid even for deep mirrors, where the aperture radius approaches the radius of curvature. We apply this result to micro-fabricated mirrors whose size scales are in the range of tens to hundreds of wavelengths, and show that sub-wavelength spot sizes can be achieved. This opens up the possibility of scalable arrays of tightly focused optical dipole traps without the need for high-performance optical systems.