1,549 research outputs found
Phase-change Nanophotonics
Phase-change materials, including metals, semiconductors and liquid crystals, have played a key role in the evolution of active nanophotonic and plasmonic functionalities. They present unique opportunities at the nano- (i.e. subwavelength) scale as a source of optical nonlinearity and a platform for high-contrast, low-energy electro-and all-optical switching / memory devices. I will review Southampton’s work in this field: from the demonstration of exceptionally large (including metamaterial-enhanced) phase-change nonlinearities underpinned by light-induced, surface-mediated structural transitions in confined gallium; through the harnessing of non-volatile optically-induced amorphous/crystalline transitions in chalcogenides (such as Ge:Sb:Te) to realize plasmonic hybrid and all-dielectric switchable and laser re-writable metasurfaces; to the recent revelation that germanium and bismuth-based chalcogenide alloys can themselves present switchable and compositionally-tunable plasmonic properties in the UV-VIS spectral range
Coherent control of Snell's law at metasurfaces
It was recently demonstrated that the well-known Snell's law must be corrected for phase gradient metasurfaces to account for their spatially varying phase, leading to normal and anomalous transmission and reflection of light on such metasurfaces. Here we show that the efficiency of normal and anomalous transmission and reflection of light can be controlled by the intensity or phase of a second coherent wave. The phenomenon is illustrated using gradient metasurfaces based on V-shaped and rectangular apertures in a metal film. This coherent control effect can be exploited for wave front shaping and signal routing
Controlling light with light using coherent meta-devices: all-optical transistor, summator and invertor
Although vast amounts of information are conveyed by photons in optical
fibers, the majority of data processing is performed electronically, creating
the infamous 'information bottleneck' and consuming energy at an increasingly
unsustainable rate. The potential for photonic devices to directly manipulate
light remains unfulfilled due largely to a lack of materials with strong, fast
optical nonlinearities. In this paper, we show that small-signal amplifier,
summator and invertor functions for optical signals may be realized using a
four-port device that exploits the coherent interaction of beams on a planar
plasmonic metamaterial, assuming no intrinsic nonlinearity. The redistribution
of energy among ports can be coherently controlled at the single photon level,
with THz bandwidth and without introducing signal distortion, thereby
presenting powerful opportunities for novel optical data processing
architectures, complexity oracles and the locally coherent networks that are
becoming part of the mainstream telecommunications agenda
Coherent control of light-matter interactions in polarization standing waves
We experimentally demonstrate that standing waves formed by two coherent counter-propagating light waves can take a variety of forms, offering new approaches to the interrogation and control of polarization-sensitive light-matter interactions in ultrathin (subwavelength thickness) media. In contrast to familiar energy standing waves, polarization standing waves have constant electric and magnetic energy densities and a periodically varying polarization state along the wave axis. counterintuitively, anisotropic ultrathin (meta)materials can be made sensitive or insensitive to such polarization variations by adjusting their azimuthal angle
Ultrafast all-optical switching via coherent modulation of metamaterial absorption
We report on the demonstration of a femtosecond all-optical modulator
providing, without nonlinearity and therefore at arbitrarily low intensity,
ultrafast light-by-light control. The device engages the coherent interaction
of optical waves on a metamaterial nanostructure only 30 nm thick to
efficiently control absorption of near-infrared (750-1040 nm) femtosecond
pulses, providing switching contrast ratios approaching 3:1 with a modulation
bandwidth in excess of 2 THz. The functional paradigm illustrated here opens
the path to a family of novel meta-devices for ultra-fast optical data
processing in coherent networks.Comment: 5 pages, 4 figure
Intrinsic optical bistability in nanomechanical metamaterials at milliwatt power levels
We report the first demonstration of optical bistability in nanomechanical metamaterials - arrays of plasmonic or dielectric resonators on flexible nano-membranes. Bistability results from the nonlinearity of the near-field forces induced by light
All-dielectric free-electron-driven holographic light sources
It has recently been shown that holographically nanostructured surfaces can
be employed to control the wavefront of (predominantly plasmonic)
optical-frequency light emission generated by the injection of medium-energy
electrons into a gold surface. Here we apply the concept to manipulation of the
spatial distribution of transition radiation emission from
high-refractive-index dielectric/semiconductor target materials, finding that
concomitant incoherent luminescent emission at the same wavelength is
unperturbed by holographic surface-relief structures, and thereby deriving a
means of discriminating between the two emission components.Comment: 5 pages, 3 figure
Photonic Metamaterial Analogue of a Continuous Time Crystal
Time crystals are an eagerly sought phase of matter with broken
time-translation symmetry. Quantum time crystals with discretely broken
time-translation symmetry have been demonstrated in trapped ions, atoms and
spins while continuously broken time-translation symmetry has been observed in
an atomic condensate inside an optical cavity. Here we report that a classical
metamaterial nanostructure, a two-dimensional array of plasmonic metamolecules
supported on flexible nanowires, can be driven to a state possessing all of the
key features of a continuous time crystal: continuous coherent illumination by
light resonant with the metamolecules' plasmonic mode triggers a spontaneous
phase transition to a superradiant-like state of transmissivity oscillations,
resulting from many-body interactions among the metamolecules, characterized by
long-range order in space and time. The phenomenon is of interest to the study
of dynamic classical many-body states in the strongly correlated regime and
applications in all-optical modulation, frequency conversion and timing.Comment: 10 pages, 6 figure
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