8,814 research outputs found
Nonlinear metal-dielectric nanoantennas for light switching and routing
We introduce a novel hybrid metal-dielectric nanoantenna composed of
dielectric (crystalline silicon) and metal (silver) nanoparticles. A
high-permittivity dielectric nanoparticle allows to achieve effective light
harvesting, and nonlinearity of a metal nanoparticle controls the radiation
direction. We show that the radiation pattern of such a nanoantenna can be
switched between the forward and backward directions by varying only the light
intensity around the level of 11 MW/cm, with the characteristic switching
time of 260 fs.Comment: 9 pages, 5 figures, submitted to New J. Phy
Plasmonic Optical Tweezers based on Nanostructures: fundamentals, advances and prospects
The ability of metallic nanostructures to confine light at the sub-wavelength
scale enables new perspectives and opportunities in the field of
nanotechnology. Making use of this unique advantage, nano-optical trapping
techniques have been developed to tackle new challenges in a wide range of
areas from biology to quantum optics. In this work, starting from basic
theories, we present a review of research progress in near-field optical
manipulation techniques based on metallic nanostructures, with an emphasis on
some of the most promising advances in molecular technology, such as the
precise control of single-biomolecules. We also provide an overview of possible
future research directions of nano-manipulation techniques.Comment: 19 page
Plasmonic-photonic crystal coupled nanolaser
We propose and demonstrate a hybrid photonic-plasmonic nanolaser that
combines the light harvesting features of a dielectric photonic crystal cavity
with the extraordinary confining properties of an optical nano-antenna. In that
purpose, we developed a novel fabrication method based on multi-step
electron-beam lithography. We show that it enables the robust and reproducible
production of hybrid structures, using fully top down approach to accurately
position the antenna. Coherent coupling of the photonic and plasmonic modes is
highlighted and opens up a broad range of new hybrid nanophotonic devices
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Precision manipulation of organic and inorganic nanoentities for enhanced optical biodetection at deterministic positions
In the last decade, considerable research interests are focused on applying semiconductor quantum dots (QDs) for bioimaging, sensing, and therapeutic delivery. Compared to traditional organic dyes, semiconductor QDs exhibit higher fluorescent brightness, better resistance to photo-bleaching, tunable sizes/colors, wider absorption peak and larger stokes shifts. However, the applications of QDs as biosensors are still largely conducted in bulk colloidal suspensions, which present considerable difficulties in sensing a minute amount of bioanalyte. It is highly desirable if the QDs can be registered at designated locations for position-predicable optical analysis and sensing. Raman scattering spectroscopy has been utilized to unambiguously identify molecules based on their intrinsic vibrational "fingerprint" states. However, due to the relatively small Raman scattering cross-section, the intensity of Raman signal is usually 1/10ⶠof that of Rayleigh scattering. The recent discovery of Surface enhanced Raman scattering (SERS) dramatically improves the Raman signal and rejuvenates this field. An enhancement factor (EF) as high as 10ÂčÂČ have been reported, which can readily detect various single molecules, essential for early-stage disease detection, warfare agent detection, environmental pollutant detection, and biomolecule detection. However, SERS substrates with such high EF usually suffer from reproducibility and uniformity issues. Moreover, SERS detection is still largely conducted in a seek-and-find manner which substantially limits the detection efficiency. Most SERS detections are carried out by drying analyte solutions on SERS substrates to force molecules to attach to hotspots before the detection. The employed drying methods can be different among individual research groups. Quantitative comparison of these results should be conducted carefully. It is highly desirable to directly detect molecules in suspension to accurately evaluate the performances of different SERS substrates. However, when directly measuring SERS signals of molecules in suspension, due to the inefficient diffusion based binding process, much less molecules can closely interact with hot spots compared to those on dried SERS samples. As a result, direct SERS detection from suspension can often be less sensitive by a few orders of magnitudes compares to those in dried condition. It is of great interest to investigate new mechanisms to detect analyte molecules directly from analyte solutions with high sensitivity. In this research, I rationally designed and synthesized various types of nanostructures, including ZnO, Si, and Au nanowires, ZnO nanosuperstructures, and hybrid nanocapsules. Such materials have unique optical/plasmonic properties and could be used in various applications, particularly in biochemical sensing. Two types of optical nanobiosensors have been designed, fabricated, characterized, and investigated. They are fluorescence-based QD-on-nanowire assemblies and SERS-photonic-crystal hybrid nanosensors. The QD-on-nanowire florescent nanosensors operated uniquely by focusing analyte molecules to the assembled QDs on tips of nanowires before detection via specific biochemical conjugation. Molecules, such as biotin, can be revealed unambiguously in a location deterministic manner with substantially enhanced sensitivity. In the development of SERS-photonic-crystal hybrid nanosensors, two enhancement mechanisms, including guided-mode resonance (GMR) and electrokinetic effect, were studied and applied in improving the sensitivity and efficiency of molecule detection, respectively. Such a hybrid device has been proposed and studied for the first time, which can readily improve the detection sensitivity by a robust 4-5 times in addition to the 10âč-10Âčâ° SERS enhancement. This dissertation work, exploring innovative materials design, synthesis, and manipulation, has made an important forward step in the next-generation biochemical detection platform.Materials Science and Engineerin
Magneto-optical response enhanced by Mie resonances in nanoantennas
Control of light by an external magnetic field is one of the important
methods for modulation of its intensity and polarisation. Magneto-optical
effects at the nanoscale are usually observed in magnetophotonic crystals,
nanostructured hybrid materials or magnetoplasmonic crystals. An indirect
action of an external magnetic field (e.g. through the Faraday effect) is
explained by the fact that natural materials exhibit negligible magnetism at
optical frequencies. However, the concept of metamaterials overcome this
limitation imposed by nature by designing artificial subwavelength meta-atoms
that support a strong magnetic response, usually termed as optical magnetism,
even when they are made of nonmagnetic materials. The fundamental question is
what would be the effect of the interaction between an external magnetic field
and an optically-induced magnetic response of metamaterial structures. Here we
make the first step toward answering this fundamental question and demonstrate
the multifold enhancement of the magneto-optical response of nanoantenna
lattices due to the optical magnetism.Comment: 7 pages, 5 figure
Near-field microscopy with a scanning nitrogen-vacancy color center in a diamond nanocrystal: A brief review
We review our recent developments of near-field scanning optical microscopy
(NSOM) that uses an active tip made of a single fluorescent nanodiamond (ND)
grafted onto the apex of a substrate fiber tip. The ND hosting a limited number
of nitrogen-vacancy (NV) color centers, such a tip is a scanning quantum source
of light. The method for preparing the ND-based tips and their basic properties
are summarized. Then we discuss theoretically the concept of spatial resolution
that is achievable in this special NSOM configuration and find it to be only
limited by the scan height over the imaged system, in contrast with the
standard aperture-tip NSOM whose resolution depends critically on both the scan
height and aperture diameter. Finally, we describe a scheme we have introduced
recently for high-resolution imaging of nanoplasmonic structures with ND-based
tips that is capable of approaching the ultimate resolution anticipated by
theory.Comment: AD, AC, OM, MB and SH wish to dedicate this brief review article to
their co-author and colleague Yannick Sonnefraud who passed away in September
2014. Yannick initiated this research in 200
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