Locking lasers with large FM noise to high Q cavities

We have demonstrated that an external-cavity diode laser can be directly locked to a high Q cavity. Lock can be acquired with a conventional analog servo even though the laser frequency sweeps through the cavity resonance in less than the cavity build-up time. We discuss the distortions of the Pound-Drever-Hall error signals in this regime and experimentally and theoretically show that a servo can acquire lock. We discuss a model of lock acquisition and experimentally show that the capture range is in fact much larger than that predicted from a linear model