Toward nanophotonic platforms for solid-state $^{229}$Th nuclear clocks

TL;DR

This paper proposes a nanophotonic platform embedding $^{229}$Th in high-Q fluoride resonators to develop a compact, solid-state nuclear clock, enhancing nuclear excitation via resonant optical modes.

Contribution

It introduces a novel approach combining nanophotonics and nuclear physics to realize a scalable, chip-scale nuclear frequency standard based on $^{229}$Th.

Findings

Resonant field build-up enhances nuclear excitation rates.

Implantation of thorium in fluoride resonators is feasible.

Modeling outlines a technological roadmap for future development.

Abstract

While the $^{229}$Th nuclear isomer has recently been observed and laser-excited, converting optical nuclear manipulation into a chip-scale solid-state frequency standard remains an open challenge. Here, we present a nanophotonic platform to realize an all-solid-state nuclear clock based on the low-energy isomeric transition of $^{229}$Th embedded in high-$Q$ fluoride photonic resonators. By coupling ensembles of thorium nuclei to confined optical modes, we show that resonant field build-up in the cavity can substantially enhance the nuclear excitation rate, enabling optical interrogation at practical laser intensities. We model the nuclei-photon interaction dynamics and outline a technological roadmap toward addressing this challenge, including resonator fabrication in fluoride crystals, thorium implantation, nuclear excitation with integrated lasers, and on-chip detection of vacuum-ultraviolet photons. As an initial proof of concept, we implant a crystalline fluoride whispering-gallery-mode resonator with $^{229}$Th and assess the impact of implantation-induced damage on resonator performance. Our platform leverages recent advances in materials integration and nanophotonics to chart a realistic route toward compact and scalable nuclear frequency standards.