Giant angular dispersion mediated by plasmonic modal competition

We report on the modal competition mediated angular dispersion by heterogeneously coupled plasmonic waveguides. By varying the wavelength of the excitation, the surface waves propagate alongside the upper and lower interfaces can be manipulated in coupled, decoupled, and cutoff regimes. Depending on the coupling states, the output beam can be steered between +15° and -17° for wavelength from λ = 695 nm to λ = 675 nm. The maximum achieved angular dispersion can be as large as 2.1°/nm. This finding may revolutionize current design concept of spectrometers, providing a significant way to scale down the form factor further into nano-size.