Autler-Townes splitting via frequency upconversion at ultra-low power levels in cold $^{87}$Rb atoms using an optical nanofiber

TL;DR

This paper demonstrates ultra-low power frequency upconversion and Autler-Townes splitting in cold rubidium atoms using an optical nanofiber, enabling precise nonlinear optical studies with minimal power.

Contribution

It introduces a novel method for observing Autler-Townes splitting via frequency upconversion at sub-nanowatt power levels in cold rubidium atoms using an optical nanofiber.

Findings

Observation of 420 nm photon generation at sub-nW powers

Direct measurement of Rabi frequency via Autler-Townes splitting

Highlights advantages of fibered systems for nonlinear atomic optics

Abstract

The tight confinement of the evanescent light field around the waist of an optical nanofiber makes it a suitable tool for studying nonlinear optics in atomic media. Here, we use an optical nanofiber embedded in a cloud of laser-cooled 87Rb for near-infrared frequency upconversion via a resonant two-photon process. Sub-nW powers of the two-photon beams, at 780 nm and 776 nm, co-propagate through the optical nanofiber and generation of 420 nm photons is observed. A measurement of the Autler-Townes splitting provides a direct measurement of the Rabi frequency of the 780 nm transition. Through this method, dephasings of the system can be studied. In this work, the optical nanofiber is used as an excitation and detection tool simultaneously, and it highlights some of the advantages of using fully fibered systems for nonlinear optics with atoms.