Speaker
Description
The first low-energy nuclear excited state of thorium-229 has gained an increasing interest since direct laser excitation have been demonstrated [1] and quickly confirmed in various solid-state experiments. This unique transition of the thorium isotope offers many applications, including a highly accurate nuclear clock, and a new testbed for physics beyond the standard model
Still, one challenging key ingredient for a high-accuracy nuclear clock is a Hz-scale, narrow-linewidth laser source for the resonance wavelength of 148.4 nm. Different concepts for such a light source like high-harmonic generation of a femtosecond laser frequency-comb, four-wave mixing in gases or metallic vapors, or all-solid-state approach are under development.
Here, we report the development of an all-solid-state CW laser system for the Th-229 nuclear transition, based on three sequential SHG steps starting from a diode laser at 1187 nm. The frequency doubling of laser radiation at 297 nm is obtained by using random quasi-phase matching in strontium tetraborate (SBO) [2]. The resulting power spectral density is comparable to that of previous laser nuclear excitation experiments [1]. We will discuss the prospects for the nuclear excitation in Th-229 doped crystals using this source.
[1] J. Tiedau, M. Okhapkin, K. Zhang, et al., Phys. Rev. Lett. 132, 182501 (2024).
[2] P. Trabs, F. Noack, A. S. Aleksandrovsky, et al., Opt. Lett. 41, 618 (2016).