30 research outputs found
Hyper-Selective Plasmonic Color Filters
The subwavelength mode volumes of plasmonic filters are well matched to the
small size of state-of-the-art active pixels (~ 1 {\mu}m) in CMOS image sensor
arrays used in portable electronic devices. Typical plasmonic filters exhibit
broad (> 100 nm) transmission bandwidths. Dramatically reducing the peak width
of filter transmission spectra would allow for the realization of CMOS
hyperspectral imaging arrays, which demand the FWHM of transmission peaks to be
less than 30 nm. We find that the design of 5 layer
metal-insulator-metal-insulator-metal structures gives rise to multi-mode
interference phenomena that suppresses spurious transmission features gives
rise to a single narrow transmission band with FWHM as small as 17 nm. The
transmission peaks of these multilayer slot-mode plasmonic filters (MSPFs) can
be systematically varied throughout the visible and near infrared spectrum, so
the same basic structure can serve as a filter over a large range of
wavelengths.Comment: 18 pages, 7 figure
PlasMOStor: A metal-oxide-Si field effect plasmonic modulator
Realization of chip-based all-optical and optoelectronic computational networks will require ultracompact Si-compatible modulators, ideally comprising dimensions, materials, and functionality similar to electronic complementary metal−oxide−semiconductor (CMOS) components. Here we demonstrate such a modulator, based on field-effect modulation of plasmon waveguide modes in a MOS geometry. Near-infrared transmission between an optical source and drain is controlled by a gate voltage that drives the MOS into accumulation. Using the gate oxide as an optical channel, electro-optic modulation is achieved in device volumes of half of a cubic wavelength with femtojoule switching energies and the potential for gigahertz modulation frequencies
Plasmonic Nanostructure Design for Efficient Light Coupling into Solar Cells
We demonstrate that subwavelength scatterers can couple sunlight into guided modes in thin film Si and GaAs plasmonic solar cells whose back interface is coated with a corrugated metal film. Using numerical simulations, we find that incoupling of sunlight is remarkably insensitive to incident angle, and that the spectral features of the coupling efficiency originate from several different resonant phenomena. The incoupling cross section can be spectrally tuned and enhanced through modification of the scatterer shape, semiconductor film thickness, and materials choice. We demonstrate that, for example, a single 100 nm wide groove under a 200 nm Si thin film can enhance absorption by a factor of 2.5 over a 10 μm area for the portion of the solar spectrum near the Si band gap. These findings show promise for the design of ultrathin solar cells that exhibit enhanced absorption
The new "p-n junction": Plasmonics enables photonic access to the nanoworld
Since the development of the light microscope in the 16th century, optical device size and performance have been limited by diffraction. Optoelectronic devices of today are much bigger than the smallest electronic devices for this reason. Achieving control of light-material interactions for photonic device applications at the nanoscale requires structures that guide electromagnetic energy with subwavelength-scale mode confinement. By converting the optical mode into nonradiating surface plasmons, electromagnetic energy can be guided in structures with lateral dimensions of less than 10% of the free-space wavelength. A variety of methods-including electron-beam lithography and self-assembly-have been used to construct both particle and planar plasmon waveguides. Recent experimental studies have confirmed the strongly coupled collective plasmonic modes of metallic nanostructures. In plasmon waveguides consisting of closely spaced silver rods, electromagnetic energy transport over distances of 0.5 mu m has been observed. Moreover, numerical simulations suggest the possibility of multi-centimeter plasmon propagation in thin metallic stripes. Thus, there appears to be no fundamental scaling limit to the size and density of photonic devices, and ongoing work is aimed at identifying important device performance criteria in the subwavelength size regime. Ultimately, it may be possible to design an entire class of subwavelength-scale optoelectronic components (waveguides, sources, detectors, modulators) that could form the building blocks of an optical device technology-a technology scalable to molecular dimensions, with potential imaging, spectroscopy, and interconnection applications in computing, communications, and chemical/biological detection
Universal optical transmission features in periodic and quasiperiodic hole arrays
We investigate the influence of array order in the optical transmission properties of subwavelength hole arrays, by comparing the experimental spectral transmittance of periodic and quasiperiodic hole arrays as a function of frequency. We find that periodicity and long-range order are not necessary requirements for obtaining enhanced and suppressed optical transmission, provided short-range order is maintained. Transmission maxima and minima are shown to result, respectively, from constructive and destructive interference at each hole, between the light incident upon and exiting from a given hole, and surface plasmon polaritons (SPPs) arriving from individual neighboring holes. These SPPs are launched along both illuminated and exit surfaces, by diffraction of the incident and emerging light at the neighboring individual subwavelength holes. By characterizing the optical transmission of a pair of subwavelength holes as a function of hole-hole distance, we demonstrate that a subwavelength hole can launch SPPs with an efficiency up to 35%, and with an experimentally determined launch phase φ = π/2, for both input-side and exit-side SPPs. This characteristic phase has a crucial influence on the shape of the transmission spectra, determining transmission minima in periodic arrays at those frequencies where grating coupling arguments would instead predict maxima
Electrooptic Modulation in Thin Film Barium Titanate Plasmonic Interferometers
We demonstrate control of the surface plasmon polariton wavevector in an active metal−dielectric plasmonic interferometer by utilizing electrooptic barium titanate as the dielectric layer. Arrays of subwavelength interferometers were fabricated from pairs of parallel slits milled in silver on barium titanate thin films. Plasmon-mediated transmission of incident light through the subwavelength slits is modulated by an external voltage applied across the barium titanate thin film. Transmitted light modulation is ascribed to two effects, electrically induced domain switching and electrooptic modulation of the barium titanate index
Electronic modulation of infrared emissivity in graphene plasmonic resonators
Electronic control of blackbody emission from graphene plasmonic resonators
on a silicon nitride substrate is demonstrated at temperatures up to 250 C. It
is shown that the graphene resonators produce antenna-coupled blackbody
radiation, manifest as narrow spectral emission peaks in the mid-IR. By
continuously varying the nanoresonators carrier density, the frequency and
intensity of these spectral features can be modulated via an electrostatic
gate. We describe these phenomena as plasmonically enhanced radiative emission
originating both from loss channels associated with plasmon decay in the
graphene sheet and from vibrational modes in the SiNx.Comment: 17 pages, 6 figure
Experimental Demonstration of >230{\deg} Phase Modulation in Gate-Tunable Graphene-Gold Reconfigurable Mid-Infrared Metasurfaces
Metasurfaces offer significant potential to control far-field light
propagation through the engineering of amplitude, polarization, and phase at an
interface. We report here phase modulation of an electronically reconfigurable
metasurface and demonstrate its utility for mid-infrared beam steering. Using a
gate-tunable graphene-gold resonator geometry, we demonstrate highly tunable
reflected phase at multiple wavelengths and show up to 237{\deg} phase
modulation range at an operating wavelength of 8.50 {\mu}m. We observe a smooth
monotonic modulation of phase with applied voltage from 0{\deg} to 206{\deg} at
a wavelength of 8.70 {\mu}m. Based on these experimental data, we demonstrate
with antenna array calculations an average beam steering efficiency of 50% for
reflected light for angles up to 30{\deg}, relative to an ideal metasurface,
confirming the suitability of this geometry for reconfigurable mid-infrared
beam steering devices
High Spectral Resolution Plasmonic Color Filters with Subwavelength Dimensions
Rapid advances in image sensor technology have generated a mismatch between the small size of image sensor pixels and the achievable filter spectral resolution. This mismatch has prevented the realization of chip-based image sensors with simultaneously high spatial and spectral resolution. We report here a concept that overcomes this trade-off, enabling high spectral resolution (transmission FWHM <31 nm) filters with subwavelength dimensions operating at optical and near-infrared wavelengths. An inverse design methodology was used to realize a new type of plasmonic cavity that efficiently couples an in-plane Fabry–Perot resonator to a single plasmonic slit that supports surface plasmon polaritons. This design principle, combined with a new metal imprinting method that yields metallic nanostructures with both top and bottom surfaces that are extremely smooth, enabled demonstration of high spectral resolution transmission filters with smaller area than any previously reported