Enhanced laser frequency stabilization to a high-finesse cavity through a combined feed-back and feed-forward...

We demonstrate a novel and simple approach for laser frequency stabilization by implementing a combined feed-back + feed-forward scheme where the bulk of the noise reduction is performed by modulators that are external to the laser source. Our scheme produces a tunable and stabilized output beam having optical power comparable to the laser output and without any residual frequency modulation while retaining tunability of the laser frequency relative to the chosen reference, in our case a stable high-finesse optical cavity. The performance of the feed-forward loop is limited by the time delay introduced by the frequency shifter that applies the correction. The implemented setup only requires a few additional standard components compared to typical Pound-Drever-Hall locking schemes and it can be applied to laser sources ranging from near-infrared to near-UV. The high degree of versatility combined with good power efficiency and optical purity make the proposed solution a valid alternative to other methods that require the use of more complex electronics and optoelectronic systems.