Shaping the fluorescent emission by lattice resonances in plasmonic crystals of nanoantennas

We demonstrate that the emission of light by fluorescent molecules in the proximity of periodic arrays of nanoantennas or plasmonic crystals can be strongly modified when the arrays are covered by a dielectric film. The coupling between localized surface plasmon resonances and photonic states leads to surface modes which increase the density of optical states and improve light extraction. Excited dye molecules preferentially decay radiatively into these modes, exhibiting an enhanced and directional emission.Comment: 5 figure

Long-range surface polaritons in ultra-thin films of silicon

We present an experimental and theoretical study of the optical excitation of long-range surface polaritons supported by thin layers of amorphous silicon (a-Si). The large imaginary part of the dielectric constant of a-Si at visible and ultraviolet (UV) frequencies allows the excitation of surface polariton modes similar to long-range surface plasmon polaritons on metals. Propagation of these modes along considerable distances is possible because the electric field is largely excluded from the absorbing thin film. We show that by decreasing the thickness of the Si layer these excitations can be extended up to UV frequencies, opening the possibility to surface polariton UV optics compatible with standard Si technology

Effective fuel temperature of wwer-1000

The main temperature characteristics of a pressurized water reactor are distinguished, supporting its safety and reliable operation. The special role of the uranium fuel effective temperature is emphasized and the accuracy of the analytical determination of the power effect is increased. The calculation of the temperature distribution along the radius of the fuel rod was carried out taking into account the temperature dependence of the thermal conductivity UO2. The design procedure was corrected for using the Finca-Ronchi dependence for the thermal conductivity of 95% density of the theoretical one

Ultrafast optical switching of the THz transmission through metallic subwavelength hole arrays

Euan Hendry, Matthew J. Lockyear, J. Gómez Rivas, L. Kuipers, and M. Bonn, Physical Review B, Vol. 75, article 235305 (2007). "Copyright © 2007 by the American Physical Society."We demonstrate ultrafast optical switching of the transmission of terahertz radiation through a metal grating with subwavelength holes. By fabricating the grating on a semiconductor silicon substrate, we are able to control the grating transmission intensity by varying the photodoping level of the silicon and thereby the resonant coupling to the metal grating. As such, we are able to switch the transmission on picosecond time scales with low visible light intensities, observing a factor of 2–5 improvement in photomodulation efficiency at resonance wavelengths over a bare silicon surface

Optical control over transmission of terahertz radiation through arrays of subwavelength holes of varying size

Thomas Henry Isaac, J. Gómez Rivas, and Euan Hendry, Physical Review B, Vol. 80, article 193412 (2009). "Copyright © 2009 by the American Physical Society."We modulate the transmission of terahertz (THz) radiation through periodic arrays of subwavelength holes in a metallic film by using pulses of visible-wavelength light to photoexcite the semiconducting substrate of the hole arrays. By varying the photodoping level of the semiconductor we are able to switch off the resonant transmission of THz radiation through the array. By varying the size of the holes, we demonstrate the crucial role that surface modes play in the resonant transmission and ultimately in the photomodulation behavior of these structures. We demonstrate that the surface-wave transmission mechanism can allow for very efficient optical modulation of radiation transmission

Surface plasmon mediated transmission of subwavelength slits at THz frequencies

T. H. Isaac, J. Gómez Rivas, J. Roy Sambles, William L. Barnes, and Euan Hendry, Physical Review B, Vol. 77, article 113411 (2008). "Copyright © 2008 by the American Physical Society."We present measurements and a numerical modeling that elucidate the role of surface plasmons in the resonant transmission of a subwavelength slit in a conducting material. By using THz time domain spectroscopy, we determine the Fabry–Pérot transmission resonances for a single slit formed from a wafer of a semiconductor with a surface plasma frequency in the THz frequency range. We measure large redshifts in the resonant frequencies close to the surface plasma frequency, which are 50% lower than the resonance frequencies expected well below the surface plasma frequency. This is an effect attributed to the coupling of plasmons on the adjacent surfaces of the slit

Time-resolved broadband analysis of slow-light propagation and superluminal transmission of electromagnetic waves in three-dimensional photonic crystals

A time-resolved analysis of the amplitude and phase of THz pulses propagating through three-dimensional photonic crystals is presented. Single-cycle pulses of THz radiation allow measurements over a wide frequency range, spanning more than an octave below, at and above the bandgap of strongly dispersive photonic crystals. Transmission data provide evidence for slow group velocities at the photonic band edges and for superluminal transmission at frequencies in the gap. Our experimental results are in good agreement with finite-difference-time-domain simulations.Comment: 7 pages, 11 figure