Experimental demonstration of dynamic thermal regulation using vanadium dioxide thin films.

We present an experimental demonstration of passive, dynamic thermal regulation in a solid-state system with temperature-dependent thermal emissivity switching. We achieve this effect using a multilayered device, comprised of a vanadium dioxide (VO) thin film on a silicon substrate with a gold back reflector. We experimentally characterize the optical properties of the VO film and use the results to optimize device design.

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 in CMOS image sensor arrays used in portable electronic devices. Typical plasmonic filters exhibit broad (> 100 nm) transmission bandwidths suitable for RBG or CMYK color filtering. Dramatically reducing the peak width of filter transmission spectra would allow for the realization of CMOS image sensors with multi- and hyperspectral imaging capabilities.

Experimental Demonstration of >230° 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 the amplitude, polarization, and phase at an interface. We report here the 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° phase modulation range at an operating wavelength of 8.

Electronic modulation of infrared radiation in graphene plasmonic resonators.

All matter at finite temperatures emits electromagnetic radiation due to the thermally induced motion of particles and quasiparticles. Dynamic control of this radiation could enable the design of novel infrared sources; however, the spectral characteristics of the radiated power are dictated by the electromagnetic energy density and emissivity, which are ordinarily fixed properties of the material and temperature. Here we experimentally demonstrate tunable electronic control of blackbody emission from graphene plasmonic resonators on a silicon nitride substrate.

Vanadium dioxide based plasmonic modulators.

Actively tunable metal-insulator-metal waveguides that employ vanadium dioxide films as the active medium are analyzed numerically. Vanadium dioxide exhibits strong contrast between the optical properties of its insulating and metallic phases. In particular, the large optical absorption in the metallic phase makes it straightforward to implement broadband attenuation modulators and switches, but this strong loss can also complicate the design of other types of devices.

Frequency tunable near-infrared metamaterials based on VO2 phase transition.

Engineering metamaterials with tunable resonances from mid-infrared to near-infrared wavelengths could have far-reaching consequences for chip based optical devices, active filters, modulators, and sensors. Utilizing the metal-insulator phase transition in vanadium oxide (VO(2)), we demonstrate frequency-tunable metamaterials in the near-IR range, from 1.5 - 5 microns.

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.

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.

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.

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.

Plasmonic modes of annular nanoresonators imaged by spectrally resolved cathodoluminescence.

We report the observation of plasmonic modes of annular resonators in nanofabricated Ag and Au surfaces that are imaged by spectrally resolved cathodoluminescence. A highly focused 30 keV electron beam is used to excite localized surface plasmons that couple to collective resonant modes of the nanoresonators. We demonstrate unprecedented resolution of plasmonic mode excitation and by combining these observations with full-field simulations find that cathodoluminescence in plasmonic nanostructures is most efficiently excited at positions corresponding to antinodes in the modal electric field intensity.