X-ray frequency combs from optically controlled resonance fluorescence

TL;DR

This paper proposes a method to generate x-ray frequency combs by imprinting optical combs onto x-ray emissions from driven ions, enabling precise x-ray frequency measurements.

Contribution

It introduces a novel scheme for producing x-ray frequency combs using a four-level ion system driven by optical and x-ray fields, extending comb technology into the x-ray regime.

Findings

Spectrum of equally spaced narrow lines predicted

Comb can be used for x-ray frequency measurement

Model valid from 100 eV to keV energies

Abstract

An x-ray pulse-shaping scheme is put forward for imprinting an optical frequency comb onto the radiation emitted on a driven x-ray transition, thus producing an x-ray frequency comb. A four-level system is used to describe the level structure of N ions driven by narrow-bandwidth x rays, an optical auxiliary laser, and an optical frequency comb. By including many-particle enhancement of the emitted resonance fluorescence, a spectrum is predicted consisting of equally spaced narrow lines which are centered on an x-ray transition energy and separated by the same tooth spacing as the driving optical frequency comb. Given a known x-ray reference frequency, our comb could be employed to determine an unknown x-ray frequency. While relying on the quality of the light fields used to drive the ensemble of ions, the model has validity at energies from the 100 eV to the keV range.