Abstract
AbstractAll-dielectric nanophotonics has become one of the most active fields of research in modern optics, largely due to the opportunities offered by the simultaneous resonant control of electric and magnetic components of light at the nanoscale. In this rapidly evolving scenario, the possibility to design artificial Huygens sources by overlapping electric and magnetic resonances has established a new paradigm in flat optics, bringing devices closer to efficient wavefront shaping with direct phase engineering at the level of the individual meta-atoms. However, their efficiency is fundamentally limited by the near-field coupling between the constituents of the metalattice. In this work, we challenge this well-conceived notion and propose an alternative concept to achieve phase control and full transmission in metasurfaces, based on the unusual properties of the nonradiating sources known as hybrid anapoles (HAs). We analyze theoretically an array of such sources and demonstrate that HAs are characterized by negligible coupling with their neighbors. Therefore, in contrast to Huygens particles, the proposed sources can operate as individual meta-atoms even in highly compact designs, becoming robust against strong disorder and preserving its characteristics when deposited on dielectric substrates. Remarkably, the phase of the transmitted wave can be modulated with negligible reflection. To illustrate the capabilities of our platform, we also utilize a disordered HA array to implement a controlled phase modulation to an ultrafast Gaussian pulse. The results of our study represent a departure from the currently established designs and open an avenue toward the realization of new devices for flat optics with unprecedented efficiency.
Highlights
Over the past few years, all-dielectric nanophotonics has become one of the most active fields in optics [1,2,3,4]
Among all the promising phenomena uncovered in this versatile research platform, directional Huygens sources, caused by the simultaneous overlap of electric and magnetic resonances with opposite parity [12, 13], hold enormous interest in the flat optics community, since two-dimensional subwavelength arrays -metasurfaces- of dielectric Huygens nanodisks with different size can imprint varying phases to an incident field, while featuring unity transmission [14], giving birth to the vibrant field of all-dielectric ‘meta-optics’
We have proposed and investigated in detail novel transparent hybrid anapoles (HAs) metasurfaces based on the unusual properties of the recently observed HA regime
Summary
While the possibility to overlap anapoles was first discussed in [39], only recently HAs were theoretically proposed and experimentally confirmed to occur in dielectric nanocylinders by inducing a degeneracy of two high order modes with different symmetry [33] Unlike conventional anapoles, they have a mixed electric and magnetic nature, in some cases displaying helicity singularities [37]. The HA particle approaches the ideal of a ‘true’ meta-atom We showcase this ability by designing highly compact silicon arrays with interparticle wall-to-wall separations of 1/8th the incident wavelength in the visible range, as well as disordered HA-metasurfaces exhibiting an identical behavior to their periodic counterparts. Modulate the phase of an ultrafast Gaussian pulse transmitted with unity efficiency from a highly disordered HA metasurface deposited on a glass substrate, solely with the knowledge of the optical response of the periodic array
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