Anapoles in dielectric metasurfaces and thermal tunabilty: theory and experiments

We present the theoretical and experimental investigation of a thermally tunable all-dielectric metasurface that sustains the non-radiating anapole source. The metasurface consists of high index metaatoms arranged in a regular pentagon with properly adjusted parameters such that the toroidal and electric dipole excitation lead to a destructive interference in the far-field. For the experimental realization we use PVC tubes of millimeter diameter that are filled with water. We place the metaatom inside a rectangular microwave waveguide and with the use of a heating belt we modify the water optical properties and measure the corresponding scattering spectra. Our findings demonstrate a wide tunability in the response of the metasurface and reveal the sensitivity of the anapole state to material losses.