Electromagnetic field confinement on sub-wavelength scales is possible at the expense of increasing optical losses. Examples are surface plasmon polaritons and resonant structures, which suffer from absorption losses and radiative outcoupling, respectively. Here, the first experimental evidence of strong electromagnetic field confinement along the lateral (out-of-plane) direction in a near lossless metasurface that supports a symmetry-protected Bound State in the Continuum is shown, which fully suppresses the radiative losses of resonant scatterers. This experimental demonstration, supported by coupled dipole calculations, is measured by a double near-field probe technique to locally excite and detect the time evolution and confinement of the electric field onto the surface, achieving an amplitude decay length from the metasurface of λ/38 at 0.39 THz.
Bibliografische notaFunding Information:
The authors acknowledge Francesco Verdelli for fabricating the samples. The authors thank Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) (Vici 680‐47‐628); Spanish MCIN/AEI/10.13039/501100011033/ and ERDF A way of making Europe & NextGenerationEU/PRTR through the grants MELODIA (PGC2018‐095777‐B‐C21) and BICPLAN6G (TED2021‐131417B‐I00) for funding.
© 2023 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH.