Ultra-broadband optical parametric generation and simultaneous RGB generation in periodically poled lithium niobate.

We report on efficient collinear optical parametric generation (OPG) with gain band ranging from 1400 to 2600 nm in a 2 cm-long periodically poled lithium niobate (PPLN) crystal. Such an ultra-broad gain band was obtained by choosing the pump wavelength at 933 nm, at which the group-velocities of the signal and the idler match near the degeneracy point. High OPG efficiency was obtained by quasi-phase matching (QPM). The ultra-broadband OPG led to efficient collinear RGB generation from a single PPLN crystal at a fixed pump wavelength. The green and red beams were found to be originating from high-order QPM sum-frequency generation between the pump and selected frequencies in the OPG band, while the blue beam was high-order QPM second-harmonic generation of the pump.