Outstanding Transmittance through Over-Wavelength-Thick Optical Plasmonic Microcavities

This work models light transmission through metal-dielectric-metal microcavities supporting Coupled Surface Plasmons (CSP). An extended Fabry-Pérot formula reveals two plasmonic resonances that merge beyond a critical cavity thickness. Remarkably, transmittance at these resonances remains high and nearly constant for thicknesses exceeding the light's penetration depth. Results at a 1 μm wavelength show over 10% transmittance up to 3.5 μm, offering new insights for photonic device design