Dispersion tuning of a narrow-linewidth picosecond OPO based on chirped quasi-phase matching with a volume Bragg grating

We report on a widely tunable synchronously-pumped picosecond OPO combining an aperiodically poled MgO-doped LiNbO3 crystal as a broadband gain medium and an intracavity axially chirped volume Bragg (VBG). Owing to the high dispersion induced by the chirped VBG, only a narrow spectral band, corresponding to a thin slice of the VBG, satisfies the synchronous-pumping condition. At a fixed position, the VBG is thus a narrow-band filtering element; variation of its position along the cavity axis enables to tune the idler wavelength over 215 nm around 3.82 mu m. Rapid continuous tuning over 150 nm in 100 ms is also demonstrated.