35 research outputs found
Cooperative behavior of quantum dipole emitters coupled to a zero-index nanoscale waveguide
We study cooperative behavior of quantum dipole emitters coupled to a
rectangular waveguide with dielectric core and silver cladding. We investigate
cooperative emission and inter-emitter entanglement generation phenomena for
emitters whose resonant frequencies are near the frequency cutoff of the
waveguide, where the waveguide effectively behaves as zero-index metamaterial.
We show that coupling emitters to a zero-index waveguide allows one to relax
the constraint on precision positioning of emitters for observing inter-emitter
entanglement generation and extend the spatial scale at which the superradiance
can be observed
Quantum optical properties of a dipole emitter coupled to an É›-near-zero nanoscale waveguide
We study quantum optical properties of a dipole emitter coupled
to a rectangular nanoscale waveguide with dielectric core and silver
cladding. We investigate enhanced spontaneous emission and the photonic
Lamb shift for emitters whose resonant frequencies are near the waveguide
frequency cutoff where the waveguide behaves as an É›-near-zero
metamaterial. Via a dyadic Green’s function-based field quantization
scheme, we calculate the photonic Lamb shift as well as the spontaneous
emission enhancement and spectrum. Using realistic parameters for typical
quantum emitters, we suggest experimentally realizable schemes to observe
relatively large photonic Lamb shifts in waveguides
Millivolt Modulation of Plasmonic Metasurface Optical Response via Ionic Conductance
A plasmonic metasurface with an electrically tunable optical response that operates at strikingly low modulation voltages is experimentally demonstrated. The fabricated metasurface shows up to 30% relative change in reflectance in the visible spectral range upon application of 5 mV and 78% absolute change in reflectance upon application of 100 mV of bias. The designed metasurface consists of nanostructured silver and indium tin oxide (ITO) electrodes which are separated by 5 nm thick alumina. The millivolt-scale optical modulation is attributed to a new modulation mechanism, in which transport of silver ions through alumina dielectric leads to bias-induced nucleation and growth of silver nanoparticles in the ITO counter-electrode, altering the optical extinction response. This transport mechanism, which occurs at applied electric fields of 1 mV nm^(−1), provides a new approach to use of ionic transport for electrical control over light–matter interactions
Universal active metasurfaces for dynamic beam steering and reconfigurable focusing at telecommunication wavelengths
We report the design and experimental demonstration of a ‘universal’ reconfigurable metasurface, which by electrical control of individual metasurface elements, enables both dynamic beam steering and reconfigurable focusing
Universal active metasurfaces for dynamic beam steering and reconfigurable focusing at telecommunication wavelengths
We report the design and experimental demonstration of a ‘universal’ reconfigurable metasurface, which by electrical control of individual metasurface elements, enables both dynamic beam steering and reconfigurable focusing
High quality factor metasurfaces for two-dimensional wavefront manipulation
The strong interaction of light with micro- and nanostructures plays a
critical role in optical sensing, nonlinear optics, active optical devices, and
quantum optics. However, for wavefront shaping, the required local control over
light at a subwavelength scale limits this interaction, typically leading to
low-quality-factor optical devices. Here, we demonstrate an avenue towards
high-quality-factor wavefront shaping in two spatial dimensions based on
all-dielectric Huygens metasurfaces by leveraging higher-order Mie resonances.
We design and experimentally realize transmissive band stop filters, beam
deflectors and radial lenses with measured quality factors in the range of
202-1475 at near-infrared wavelengths. The excited optical mode and resulting
wavefront control are both local, allowing versatile operation with finite
apertures and oblique illumination. Our results represent an improvement in
quality factor by nearly two orders of magnitude over previous localized mode
designs, and provide a design approach for a new class of compact optical
devices.Comment: 19 pages, 4 figure
Tunable all-dielectric metasurface for phase modulation of the reflected and transmitted light via permittivity tuning of indium tin oxide
We propose an electrically tunable metasurface, which can achieve relatively large phase modulation in both reflection and transmission modes (dual-mode operation). By integration of an ultrathin layer of indium tin oxide (ITO) as an electro-optically tunable material into a semiconductor-insulator-semiconductor (SIS) unit cell, we report an approach for active tuning of all-dielectric metasurfaces. The proposed controllable dual-mode metasurface includes an array of silicon (Si) nanodisks connected together via Si nanobars. These are placed on top of alumina and ITO layers, followed by a Si slab and a silica substrate. The required optical resonances are separately excited by Si nanobars in reflection and Si nanodisks in transmission, enabling highly confined electromagnetic fields at the ITO-alumina interface. Modulation of charge carrier concentration and refractive index in the ITO accumulation layer by varying the applied bias voltage leads to 240° of phase agility at an operating wavelength of 1696 nm for the reflected transverse electric (TE)-polarized beam and 270° of phase shift at 1563 nm for the transmitted transverse magnetic (TM)-polarized light. Independent and isolated control of the reflection and transmission modes enables distinctly different functions to be achieved for each operation mode. A rigorous coupled electrical and optical model is employed to characterize the carrier distributions in ITO and Si under applied bias and to accurately assess the voltage-dependent effects of inhomogeneous carrier profiles on the optical behavior of a unit cell
Array-scale inverse design of active metasurfaces
We develop an inverse design approach to optimize array architectures of reconfigurable metasurfaces and report dramatically improved beam steering performances with non-ideal antenna components. The versatility is enhanced by enabling continuous steering up to 70°