85 research outputs found
Cascaded four-wave mixing in tapered plasmonic nanoantenna
We study theoretically the cascaded four-wave mixing (FWM) in broadband
tapered plasmonic nanoantennas and demonstrate a 300-fold increase in nonlinear
frequency conversion detected in the main lobe of the nanoantenna far-field
pattern. This is achieved by tuning the elements of the nanoantenna to resonate
frequencies involved into the FWM interaction. Our findings have a potentially
broad application in ultrafast nonlinear spectroscopy, sensing, on-chip optical
frequency conversion, nonlinear optical metamaterials and photon sources
Optical Yagi-Uda nanoantennas
Conventional antennas, which are widely employed to transmit radio and TV
signals, can be used at optical frequencies as long as they are shrunk to
nanometer-size dimensions. Optical nanoantennas made of metallic or
high-permittivity dielectric nanoparticles allow for enhancing and manipulating
light on the scale much smaller than wavelength of light. Based on this
ability, optical nanoantennas offer unique opportunities regarding key
applications such as optical communications, photovoltaics, non-classical light
emission, and sensing. From a multitude of suggested nanoantenna concepts the
Yagi-Uda nanoantenna, an optical analogue of the well-established
radio-frequency Yagi-Uda antenna, stands out by its efficient unidirectional
light emission and enhancement. Following a brief introduction to the emerging
field of optical nanoantennas, here we review recent theoretical and
experimental activities on optical Yagi-Uda nanoantennas, including their
design, fabrication, and applications. We also discuss several extensions of
the conventional Yagi-Uda antenna design for broadband and tunable operation,
for applications in nanophotonic circuits and photovoltaic devices
Multifrequency broadband tapered plasmonic nanoantennas
We suggest a novel multifrequency broadband plasmonic Yagi-Uda-type
nanoantenna equipped with an array of tapered directors. Each director can be
used for the excitation of the antenna by nanoemitters matched spectrally with
the director resonant frequency and placed in the director near-field region.
Multifrequency op- eration of nanoantennas provides tremendous opportunities
for broadband emission enhancement, spectroscopy and sensing. By the principle
of reciprocity, the same tapered nanoantenna architecture can be used both as a
transmitter and/or as a receiver, thus being useful for creating a broadband
wireless communication system
Plasmonic Nanoantennas for Efficient Control of Polarization-Entangled Photon Pairs
We suggest a novel source of polarization-entangled photon pairs based on a
cross-shaped plasmonic nanoantenna driven by a single quantum dot. The
integration of the nanoantenna with a metal mirror overcomes the fundamental
tradeoff between the spontaneous emission (SE) enhancement and the extraction
efficiency typical of microcavity and nanowire-based architectures. With a
very-high extraction efficiency of entangled photons (~90%) at 1.55 um and
large SE enhancement (~90) over a broad 330 nm spectral range, the proposed
design will pave the way toward reliable integrated sources of nonclassical
light
A functional variant in the Stearoyl-CoA desaturase gene promoter enhances fatty acid desaturation in pork
There is growing public concern about reducing saturated fat intake. Stearoyl-CoA desaturase (SCD) is the lipogenic enzyme responsible for the biosynthesis of oleic acid (18:1) by desaturating stearic acid (18:0). Here we describe a total of 18 mutations in the promoter and 3′ non-coding region of the pig SCD gene and provide evidence that allele T at AY487830:g.2228T>C in the promoter region enhances fat desaturation (the ratio 18:1/18:0 in muscle increases from 3.78 to 4.43 in opposite homozygotes) without affecting fat content (18:0+18:1, intramuscular fat content, and backfat thickness). No mutations that could affect the functionality of the protein were found in the coding region. First, we proved in a purebred Duroc line that the C-T-A haplotype of the 3 single nucleotide polymorphisms (SNPs) (g.2108C>T; g.2228T>C; g.2281A>G) of the promoter region was additively associated to enhanced 18:1/18:0 both in muscle and subcutaneous fat, but not in liver. We show that this association was consistent over a 10-year period of overlapping generations and, in line with these results, that the C-T-A haplotype displayed greater SCD mRNA expression in muscle. The effect of this haplotype was validated both internally, by comparing opposite homozygote siblings, and externally, by using experimental Duroc-based crossbreds. Second, the g.2281A>G and the g.2108C>T SNPs were excluded as causative mutations using new and previously published data, restricting the causality to g.2228T>C SNP, the last source of genetic variation within the haplotype. This mutation is positioned in the core sequence of several putative transcription factor binding sites, so that there are several plausible mechanisms by which allele T enhances 18:1/18:0 and, consequently, the proportion of monounsaturated to saturated fat.This research was supported by grants from the Spanish Ministry of Science and Innovation (AGL2009-09779 and AGL2012-33529). RRF is recipient of a PhD scholarship from the Spanish Ministry of Science and Innovation (BES-2010-034607). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of manuscript
Enhancing weak optical signals using a plasmonic Yagi-Uda nanoantenna array
Nanoantennas have been used in a wide range of applications in sensing, spectroscopy, and imaging-in general, the antennas can enhance physical phenomena such as the local electric field or concentrate light in a certain direction. We have fabricated an array of 80 plasmonic Yagi-Uda nanoantennas on the cladding of an optical fiber and, by doing this, we show that the signal reaching the fast detector can be increased by a factor of 5 dB. The experiment demonstrates that plasmonic directive nanoantennas can indeed collect and concentrate electromagnetic radiation along a certain direction and eventually could be used to enhance weak signals
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