Robust suppression of high-frequency laser phase noise by adaptive Pound-Drever-Hall feedforward

As opposed to feedback, feedforward methods bring new opportunities to suppress high-frequency laser phase noise, but their performance is more susceptible to environmental perturbations, hindering broad application. Tackling the key factors for long-term stability of feedforward based on Pound-Drever-Hall (PDH) detection, the authors construct a compact circuit to adaptively control feedforward gain in response to power variations of cavity transmission. This design achieves robust suppression beyond 40 dB for megahertz noise frequencies. The compact scheme may promote the general use of reliable PDH feedforward in simple, inexpensive lasers for precision quantum control and metrology.