Power scaling of tunable, narrowband, non-resonant PPLN optical parametric oscillators

We review our recent achievements with narrowband, nanosecond, non-resonant optical parametric oscillators based on periodically-poled LiNbO3, which are pumped at 1064 nm and emit close to degeneracy in the near-IR part of the spectrum between 1860 and 2486 nm. The average output power has been scaled up to the 10-W level with tuning across 40 nm (signal) and 66 nm (idler) using transversely chirped volume Bragg gratings (VBGs) acting on the signal wave. The maximum total average output power (signal + idler) achieved with a narrowband VBG has reached 11.35 W at 20 kHz, corresponding to a conversion efficiency of 63%. In this case, the signal and idler bandwidths amount to 0.7 and 0.9 nm at ~1922 and ~2384 nm, respectively. The experimentally observed spectral narrowing is reproduced by numerical simulations based on a split-step method within the plane-wave approximation taking account pump depletion and back-conversion. Spatial effects are also incorporated in the model, taking into account the transversal intensity distributions, in order to better reproduce the input-output power characteristics.