Broadening the dynamic range of the Pound-Drever-Hall frequency stabilization technique

The Pound-Drever-Hall technique is widely used for laser frequency or optical cavity length stabilization. We propose a method to broaden its dynamic range. The conventional error signal divided by the transmission power serves as the new error signal, which increases the dynamic range in the linear regime. The use of an extended Kalman filter improves the resilience to noise when the transmitted power is low. This expands the dynamic range into the nonlinear regime and achieves a deterministic auto-lock even in the presence of a large disturbance. Such a nonlinear extension is, however, limited to an auto-lock for a previously locked state because the extended Kalman filter requires accurate prior knowledge of the initial state. For demonstration purposes, we simulate the implementation of this method for locking a ten-meter scale cavity with a single-stage suspension.