Root cause of autolocking failures at high circulating power

Identify the physical and control‑system mechanisms that prevent the Pound–Drever–Hall autolocking scheme from recapturing the cavity resonance when the near‑concentric Fabry–Pérot cavity operates above approximately 60 kW circulating power, and develop a locking strategy that anticipates rapid resonance shifts so relocking is robust at high power.

Background

The system uses a cascaded Pound–Drever–Hall autolocking architecture to acquire the cavity resonance. It relocks reliably at low circulating power (<20 kW) but often fails at >60 kW.

The authors suspect rapid radiation‑pressure and thermo‑expansion effects within microseconds of scan capture, but the exact cause is unresolved; a robust high‑power autolocking solution would improve usability and uptime of the laser phase plate.