Entangled two-photon absorption for the continuous generation of excited state populations in plasma

TL;DR

This paper explores entangled two-photon absorption (ETPA) as a continuous, lower-intensity alternative to classical methods for exciting plasma states, with potential applications in high-resolution plasma diagnostics.

Contribution

It introduces the concept of using entangled photons for continuous two-photon absorption in plasma, highlighting advantages over classical techniques and proposing a plan for experimental validation.

Findings

ETPA enables continuous excitation of plasma states with lower laser intensities.

Non-collinear entangled photon generation allows spatial localization of signals.

The paper discusses candidate transitions and experimental plans for plasma measurement.

Abstract

Entangled two-photon absorption (ETPA) may be a viable technique to continuously drive an excited state population in plasma for high-bandwidth spectroscopy measurements of localized plasma turbulence or impurity density. Classical two-photon absorption commonly requires a high-intensity, pulsed laser, but entangled photons with short entanglement time and high time correlation may allow for ETPA using a lower intensity, continuous-wave laser. Notably, ETPA with non-collinear entangled photon generation allows for cross-beam spatial localization of the absorption or fluorescence signal using a single laser source. Entangled photon generation, the ETPA cross-section, candidate transitions for an Ar-II species, and plans for a proof-of-principle measurement in a helicon plasma are discussed.