4 research outputs found
Recommended from our members
Reconfigurable Semiconductor Phased-Array Metasurfaces
Phased-array metamaterial
systems are enabling new classes of refractive
and diffractive optical elements through spatial-phase engineering.
In this article, we develop design principles for reconfigurable optical
antennas and metasurfaces. We theoretically demonstrate the tunability
of infrared scattering phase and radiation patterns in low-loss, high-index
dielectric resonators using free carrier refraction. We demonstrate
reconfigurable endfire antennas based on interference between multiple
elements. Within single resonators, we demonstrate reconfigurable
broadside antenna radiation lobes arising from interfering electric
and magnetic dipole resonances. Extending this concept to infinite
arrays, we design ideal Huygens metasurfaces with spectrally overlapping
electric and magnetic dipole resonances. By introducing free charge
carriers into these metasurfaces, we demonstrate continuously tunable
transmission phase between 0 and 2Ï€ with less than 3 dB loss
in intensity. Such tunable metasurfaces may form the basis for reconfigurable
metadevices that enable unprecedented control over the electromagnetic
wavefront
Recommended from our members
Reconfigurable Semiconductor Phased-Array Metasurfaces
Phased-array metamaterial
systems are enabling new classes of refractive
and diffractive optical elements through spatial-phase engineering.
In this article, we develop design principles for reconfigurable optical
antennas and metasurfaces. We theoretically demonstrate the tunability
of infrared scattering phase and radiation patterns in low-loss, high-index
dielectric resonators using free carrier refraction. We demonstrate
reconfigurable endfire antennas based on interference between multiple
elements. Within single resonators, we demonstrate reconfigurable
broadside antenna radiation lobes arising from interfering electric
and magnetic dipole resonances. Extending this concept to infinite
arrays, we design ideal Huygens metasurfaces with spectrally overlapping
electric and magnetic dipole resonances. By introducing free charge
carriers into these metasurfaces, we demonstrate continuously tunable
transmission phase between 0 and 2Ï€ with less than 3 dB loss
in intensity. Such tunable metasurfaces may form the basis for reconfigurable
metadevices that enable unprecedented control over the electromagnetic
wavefront
Ultrawide Thermo-optic Tuning of PbTe Meta-Atoms
Subwavelength
Mie resonators have enabled new classes of optical
antenna and nanophotonic devices and can act as the basic meta-atom
constituents of low-loss dielectric metasurfaces. In any application,
tunable Mie resonances are key to achieving a dynamic and reconfigurable
operation. However, the active tuning of these nanoantennas is still
limited and usually results in sub-linewidth resonance tuning. Here,
we demonstrate the ultrawide dynamic tuning of PbTe Mie resonators
fabricated via both laser ablation and a novel solution-processing
approach. Taking advantage of the extremely large thermo-optic (TO)
coefficient and a high refractive index of PbTe, we demonstrate high-quality
factor Mie resonances that are tuned by several linewidths with temperature
modulations as small as Δ<i>T</i> ∼ 10 K. We
reveal that the origin for this exceptional tunability is due to an
increased TO coefficient of PbTe at low temperatures. When combined
into metasurface arrays, these effects can be exploited in ultranarrow
active notch filers and metasurface phase shifters that require only
a few kelvin modulation. These findings demonstrate the enabling potential
of PbTe as a versatile, solution-processable, and highly tunable nanophotonic
material that suggests new possibilities for meta-atom paints, coatings,
and 3D metamaterials fabrication
Widely Tunable Infrared Antennas Using Free Carrier Refraction
We
demonstrate tuning of infrared Mie resonances by varying the carrier
concentration in doped semiconductor antennas. We fabricate spherical
silicon and germanium particles of varying sizes and doping concentrations.
Single-particle infrared spectra reveal electric and magnetic dipole,
quadrupole, and hexapole resonances. We subsequently demonstrate doping-dependent
frequency shifts that follow simple Drude models, culminating in the
emergence of plasmonic resonances at high doping levels and long wavelengths.
These findings demonstrate the potential for actively tuning infrared
Mie resonances by optically or electrically modulating charge carrier
densities, thus providing an excellent platform for tunable metamaterials