7,847 research outputs found
Surface-plasmon enhanced bright emission from CdSe quantum-dot nanocrystals
We obtained very bright light emission from CdSe quantum dots (QDs) by using the surface-plasmon (SP) coupling technique. 23-fold enhanced photoluminescence (PL) intensities and two-fold increased PL decay rates are observed when the QDs are located on evaporated gold films. This enhancement is not effective for CdSe cores with ZnS shells (ZnS/CdSe). The reason for this difference can be explained by using the SP dispersion diagram and by considering the SP coupling mechanism. We discuss the inherent merits and demerits of this technique to increase the emission efficiency. This technique will enable high-speed and efficient light emission for optically as well as electrically pumped light emitters
Optical emission near a high-impedance mirror
Solid state light emitters rely on metallic contacts with high
sheet-conductivity for effective charge injection. Unfortunately, such contacts
also support surface plasmon polariton (SPP) excitations that dissipate optical
energy into the metal and limit the external quantum efficiency. Here, inspired
by the concept of radio-frequency (RF) high-impedance surfaces and their use in
conformal antennas we illustrate how electrodes can be nanopatterned to
simultaneously provide a high DC electrical conductivity and high-impedance at
optical frequencies. Such electrodes do not support SPPs across the visible
spectrum and greatly suppress dissipative losses while facilitating a desirable
Lambertian emission profile. We verify this concept by studying the emission
enhancement and photoluminescence lifetime for a dye emitter layer deposited on
the electrodes
Photonic crystals for confining, guiding, and emitting light
We show that by using the photonic crystals, we can confine, guide, and emit light efficiently. By precise control over the geometry and three-dimensional design, it is possible to obtain high quality optical devices with extremely small dimensions. Here we describe examples of high-Q optical nanocavities, photonic crystal waveguides, and surface plasmon enhanced light-emitting diode (LEDs)
Recent advances in solid-state organic lasers
Organic solid-state lasers are reviewed, with a special emphasis on works
published during the last decade. Referring originally to dyes in solid-state
polymeric matrices, organic lasers also include the rich family of organic
semiconductors, paced by the rapid development of organic light emitting
diodes. Organic lasers are broadly tunable coherent sources are potentially
compact, convenient and manufactured at low-costs. In this review, we describe
the basic photophysics of the materials used as gain media in organic lasers
with a specific look at the distinctive feature of dyes and semiconductors. We
also outline the laser architectures used in state-of-the-art organic lasers
and the performances of these devices with regard to output power, lifetime,
and beam quality. A survey of the recent trends in the field is given,
highlighting the latest developments in terms of wavelength coverage,
wavelength agility, efficiency and compactness, or towards integrated low-cost
sources, with a special focus on the great challenges remaining for achieving
direct electrical pumping. Finally, we discuss the very recent demonstration of
new kinds of organic lasers based on polaritons or surface plasmons, which open
new and very promising routes in the field of organic nanophotonics
Spontaneous emission control in high-extraction efficiency plasmonic crystals
We experimentally and theoretically investigate exciton-field coupling for
the surface plasmon polariton (SPP) in waveguide-confined (WC) anti-symmetric
modes of hexagonal plasmonic crystals in InP-TiO-Au-TiO-Si heterostructures.
The radiative decay time of the InP-based transverse magnetic (TM)-strained
multi-quantum well (MQW) coupled to the SPP modes is observed to be 2.9-3.7
times shorter than that of a bare MQW wafer. Theoretically we find that 80 % of
the enhanced PL is emitted into SPP modes, and 17 % of the enhanced
luminescence is redirected into WC-anti-symmetric modes. In addition to the
direct coupling of the excitons to the plasmonic modes, this demonstration is
also useful for the development of high-temperature SPP lasers, the development
of highly integrated photo-electrical devices, or miniaturized biosensors.Comment: Spontaneous emission control in high-extraction efficiency plasmonic
crystal
Plasmon-enhanced generation of non-classical light
Strong light-matter interactions enabled by surface plasmons have given rise
to a wide range of photonic, optoelectronic and chemical functionalities. In
recent years, the interest in this research area has focused on the quantum
regime, aiming to developing ultra-compact nanoscale instruments operating at
the single (few) photon(s) level. In this perspective, we provide a general
overview of recent experimental and theoretical advances as well as near-future
challenges towards the design and implementation of plasmon-empowered quantum
optical and photo-emitting devices based on the building blocks of
nanophotonics technology: metallo-dielectric nanostructures and microscopic
light sources
Enhanced light emission from top-emitting organic light-emitting diodes by optimizing surface plasmon polariton losses
We demonstrate enhanced light extraction for monochrome top-emitting organic
light-emitting diodes (OLEDs). The enhancement by a factor of 1.2 compared to a
reference sample is caused by the use of a hole transport layer (HTL) material
possessing a low refractive index (1.52). The low refractive index reduces the
in-plane wave vector of the surface plasmon polariton (SPP) excited at the
interface between the bottom opaque metallic electrode (anode) and the HTL. The
shift of the SPP dispersion relation decreases the power dissipated into lost
evanescent excitations and thus increases the outcoupling efficiency, although
the SPP remains constant in intensity. The proposed method is suitable for
emitter materials owning isotropic orientation of the transition dipole moments
as well as anisotropic, preferentially horizontal orientation, resulting in
comparable enhancement factors. Furthermore, for sufficiently low refractive
indices of the HTL material, the SPP can be modeled as a propagating plane wave
within other organic materials in the optical microcavity. Thus, by applying
further extraction methods, such as micro lenses or Bragg gratings, it would
become feasible to obtain even higher enhancements of the light extraction.Comment: 11 pages, 6 figures, will be submitted to PR
Quantum Electrodynamic Control of Matter: Cavity-Enhanced Ferroelectric Phase Transition
The light-matter interaction can be utilized to qualitatively alter physical properties of materials. Recent theoretical and experimental studies have explored this possibility of controlling matter by light based on driving many-body systems via strong classical electromagnetic radiation, leading to a time-dependent Hamiltonian for electronic or lattice degrees of freedom. To avoid inevitable heating, pump-probe setups with ultrashort laser pulses have so far been used to study transient light-induced modifications in materials. Here, we pursue yet another direction of controlling quantum matter by modifying quantum fluctuations of its electromagnetic environment. In contrast to earlier proposals on light-enhanced electron-electron interactions, we consider a dipolar quantum many-body system embedded in a cavity composed of metal mirrors and formulate a theoretical framework to manipulate its equilibrium properties on the basis of quantum light-matter interaction. We analyze hybridization of different types of the fundamental excitations, including dipolar phonons, cavity photons, and plasmons in metal mirrors, arising from the cavity confinement in the regime of strong light-matter interaction. This hybridization qualitatively alters the nature of the collective excitations and can be used to selectively control energy-level structures in a wide range of platforms. Most notably, in quantum paraelectrics, we show that the cavity-induced softening of infrared optical phonons enhances the ferroelectric phase in comparison with the bulk materials. Our findings suggest an intriguing possibility of inducing a superradiant-type transition via the light-matter coupling without external pumping. We also discuss possible applications of the cavity-induced modifications in collective excitations to molecular materials and excitonic devices
Metallic nanostructures for efficient LED lighting
Light-emitting diodes (LEDs) are driving a shift toward energy-efficient illumination. Nonetheless, modifying the emission intensities, colors and directionalities of LEDs in specific ways remains a challenge often tackled by incorporating secondary optical components. Metallic nanostructures supporting plasmonic resonances are an interesting alternative to this approach due to their strong light–matter interaction, which facilitates control over light emission without requiring external secondary optical components. This review discusses new methods that enhance the efficiencies of LEDs using nanostructured metals. This is an emerging field that incorporates physics, materials science, device technology and industry. First, we provide a general overview of state-of-the-art LED lighting, discussing the main characteristics required of both quantum wells and color converters to efficiently generate white light. Then, we discuss the main challenges in this field as well as the potential of metallic nanostructures to circumvent them. We review several of the most relevant demonstrations of LEDs in combination with metallic nanostructures, which have resulted in light-emitting devices with improved performance. We also highlight a few recent studies in applied plasmonics that, although exploratory and eminently fundamental, may lead to new solutions in illuminatio
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