Multiplet independent resonance modes in multiplexed gratings.

Resonance modes in usual optical resonators are orthogonal, but correlated and their resonance properties cannot be independently controlled. Multiplexed gratings, consisting of multiple harmonic grating features, show multiplet resonance modes that can be independently adjusted. This offers flexibility in designing resonance characteristics for various potential applications in nonlinear optics and controlling/enhancement of light-matter interactions, e.g., to resonantly enhance the local densities of photonic modes of both the excitation and emission light in photoluminescence, which cannot be intentionally achieved with conventional resonators. Here we report the design, characteristics and experimental implementation of the multiplexed metal gratings that have doublet or triplet resonance modes. Based on numerical simulations, we investigated dependences of the resonance modes, field distributions and local field enhancements on structure features of the gratings. In implementation, we elaborated the experimental considerations, and demonstrated the consistency in structure features and their resonance characteristics for designed and as-fabricated multiplexed grating resonators.