Spanning the near-UV: Dual strong-coupling modes in an Al metasurface

The dual strong-coupling modes facilitate additional energy relaxation channels and broaden spectral enhancements offering promising applications in nanophotonics. However, the dual strong-coupling modes present significant challenges due to limited synergy among coupling types, confinement to visible and infrared excitation, and a lack of relevant studies in the ultraviolet regime, as well as limited tunability. To address these issues, we have theoretically achieved dual strong-coupling modes in both different- and same-band configurations on an Al metasurface. By adjusting the period and diameter of the Al cylinder, it is possible to span both types of dual strong-coupling modes' excitation wavelength from the near ultraviolet to a depth of 329 nm. This work provides ways to adjust coupling wavebands, modulate linewidth, and broaden spectral enhancements.