GoKawiilPTB team details 229.8 nm laser setup for thorium-229 nuclear clock feedback loop
Researchers describe a laser interrogation system built around a commercial frequency-quadrupled diode laser that reaches roughly 500 mW at 296.8 nm, used to probe a thorium-229-doped crystal sample. The setup combines offset-frequency phase locking and Pound-Drever-Hall stabilization to a reference cavity, with a photomultiplier tube detecting fluorescence signals inside a vacuum chamber, and the clock laser's frequency also compared against an optical frequency comb.
GoKawiil's interpretation of the reporting above, not reported fact.
This engineering detail matters because stabilizing a laser precisely enough to interrogate the 229Th nuclear transition is considered a key technical hurdle toward building a nuclear clock, which physicists say could rival or exceed existing atomic clocks in stability. Publishing the specific feedback architecture gives other labs a template for replicating or improving nuclear clock prototypes, potentially accelerating progress toward practical timekeeping devices based on nuclear rather than atomic transitions.
- The system uses a 500 mW, 296.8 nm laser derived from a 1,187 nm seed via frequency quadrupling.
- Dual feedback loops (offset phase lock and Pound-Drever-Hall) stabilize the clock laser to a reference cavity.
- A thorium-229-doped crystal with known isotope concentration serves as the nuclear clock reference medium.
Source: nature.com — Toscani De Col, 2026-10-07
Published there as: “A thorium-229 optical nuclear clock with feedback loop”
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