The kHz level stabilization of an intracavity doubled continuous wave optical parametric oscillator using Pound-Drever-Hall scheme

Quantum manipulation using the optical transition (³H₄→¹D₂) of Pr³⁺ embedded in solid state host materials requires a visible source emitting at 606 nm with a linewidth at the kHz level. In a previous work, the authors reported the stabilization of a continuous wave intracavity frequency doubled singly resonant optical parametric oscillator (cw-SHG-SRO) by locking it onto the side of the transmission fringe of a medium finesse Fabry-Perot (FP) cavity. In this scheme, the signal transmitted by the FP cavity was not only sensitive to any frequency fluctuation but also to any change in the source power, which can be misinterpreted as a frequency fluctuation. To overcome this limitation, the Pound-Drever-Hall (PDH) stabilization technique using a high finesse stable FP cavity seems to be the best alternative, at least, for two reasons: i) at resonance with the reference cavity, the lock signal is equal to zero, so that any laser power fluctuations will not perturbate the lock, ii) the response will not be limited by the cavity time storage of light; this allows the use of very high finesse FP cavity.