Blue-detuned evanescent field surface traps for neutral atoms based on mode interference in ultra-thin optical fibres

TL;DR

This paper introduces a new method for creating stable, micro-scale traps for cold neutral atoms near ultra-thin optical fibres using two-mode interference, enabling long trapping lifetimes and potential fiber-based quantum systems.

Contribution

It proposes a novel blue-detuned evanescent field trapping technique based on mode interference in ultra-thin fibres, with detailed analysis of trap configurations and properties.

Findings

Traps can be formed 1-200 nm from fibre surface.

Trap depths reach about 1 mK with tens of milliwatts of laser power.

Trapping lifetimes exceed 100 seconds.

Abstract

We present and analyze a novel concept for blue-detuned evanescent field surface traps for cold neutral atoms based on two-mode interference in ultra-thin optical fibres. When two or more transverse modes with the same frequency co-propagate in the fibre, their different phase velocities cause a stationary interference pattern to establish. Intensity minima of the evanescent field at any distance from the fibre surface can be created and an array of optical microtraps can thus be obtained in the evanescent field. We discuss three possible combinations of the lowest order modes, yielding traps at one to two hundred nanometres from the fibre surface which, using a few ten milliwatts of trapping laser power, have a depth on the order of 1 mK for caesium atoms and a trapping lifetime exceeding 100 seconds. The resulting trapping geometry is of particular interest because atoms in such microtrap arrays will be coupled to any additional field propagating in the fibre via the evanescent field, thereby realising ensembles of fibre-coupled atoms.