Electro-optic spectral tuning in a continuous-wave, asymmetric-duty-cycle, periodically poled LiNbO_3 optical parametric oscillator

We demonstrate electro-optic spectral tuning in a continuous-wave periodically poled ${\mathrm{LiNbO}}_3$ (PPLN) optical parametric oscillator (OPO). We achieve $8.91 {\mathrm{cm}}^{-1}$ of rapid spectral tuning, with a linear tuning rate of $2.89 {\mathrm{cm}}^{-1}/\left(\mathrm{kV}/\mathrm{mm}\right)$, by applying electric fields up to $\pm 1.5 \mathrm{kV}/\mathrm{mm}$ across the crystal while it is operating within the OPO. Intentionally poling the PPLN crystal with an asymmetric domain structure enables tuning, and numerical predictions closely match the experimental observations. The tuning is considerably larger than the typical operational bandwidth of the OPO, indicating that we are in fact shifting the gain curve of the PPLN crystal.