Nonlinear beam conversion with multi-spectral components

We characterized the intra-cavity mode patterns due to the concurrence of dual-optical parametric oscillations (OPOs) followed by second-harmonic generation (SHG) and sum-frequency generation (SFG) within a gain-modulated quasi-phase-matching nonlinear photonic crystal (QPM-NPC). The proposed device contains a bi-grating QPM period for downconversion, followed by mono- or tri-grating QPM periods for upconversion on periodically poled lithium tantalate. The pairs of infrared dual-OPO beams are found to spatially reside at the opposite sidelobes of the cavity mode, each exhibiting distinct spectral contents corresponding to the pair of (signal, idler) waves oscillating at (979, 1167) nm and (964, 1189) nm, respectively. The QPM-SHG waves at 582 and 593 nm are found to overlap with their respective OPO counterparts in the sidelobes, whereas the QPM-SFG at 588 nm wavelength is located at the center. Such spatial-spectral configurability reveals a subtle spatial overlap in the dual-OPO idlers due to wave continuity in the gain-modulated NPC, which agrees with our model calculation.