Solid-State $\rm ^{229}Th$ Nuclear Laser with Two-Photon Pumping

TL;DR

This paper proposes a novel two-photon pumping method for thorium-229 nuclear laser using a 300 nm UV-B laser, enabling room-temperature population inversion and potential realization of a nuclear laser with existing laser technology.

Contribution

It introduces an efficient two-photon pumping scheme for thorium-229, utilizing the optonuclear quadrupolar effect and ultrawide bandgap compounds, advancing nuclear laser development.

Findings

Two-photon pumping scheme achieves population inversion at room temperature.

Population inversion can be realized with Watt-level UV-B lasers.

Potential for nuclear laser development using thorium compounds.

Abstract

The radiative excitation of the 8.3 eV isomeric state of thorium-229 is an outstanding challenge due to the lack of tunable far-ultraviolet (F-UV) sources. In this work, we propose an efficient two-photon pumping scheme for thorium-229 using the optonuclear quadrupolar effect, which only requires a 300 nm UV-B pumping laser. We further demonstrate that population inversion between the nuclear isomeric and ground states can be achieved at room temperature using a two-step pumping process. The nuclear laser, which has been pursued for decades, may be realized using a Watt-level UV-B pumping laser and ultrawide bandgap thorium compounds (e.g., $\rm ThF_4$, $\rm Na_2ThF_6$, or $\rm K_2ThF_6$) as the gain medium.