Near-field light design with colloidal quantum dots for photonics and plasmonics

Colloidal quantum-dots are bright, tunable emitters that are ideal for studying near-field quantum-optical interactions. However, their colloidal nature has hindered their facile and precise placement at desired near-field positions, particularly on the structured substrates prevalent in plasmonics. Here, we use high-resolution electro-hydrodynamic printing (<100 nm feature size) to deposit countable numbers of quantum dots on both flat and structured substrates with a few nanometer precision. We also demonstrate that the autofocusing capability of the printing method enables placement of quantum dots preferentially at plasmonic hot spots. We exploit this control and design diffraction-limited photonic and plasmonic sources with arbitrary wavelength, shape, and intensity. We show that simple far-field illumination can excite these near-field sources and generate fundamental plasmonic wave-patterns (plane and spherical waves). The ability to tailor subdiffraction sources of plasmons with quantum dots provides a complementary technique to traditional scattering approaches, offering new capabilities for nanophotonics.ISSN:1530-6984ISSN:1530-699

Plasmonic films can easily be better: Rules and recipes

High-quality materials are critical for advances in plasmonics, especially as researchers now investigate quantum effects at the limit of single surface plasmons or exploit ultraviolet- or CMOS-compatible metals such as aluminum or copper. Unfortunately, due to inexperience with deposition methods, many plasmonics researchers deposit metals under the wrong conditions, severely limiting performance unnecessarily. This is then compounded as others follow their published procedures. In this perspective, we describe simple rules collected from the surface-science literature that allow high-quality plasmonic films of aluminum, copper, gold, and silver to be easily deposited with commonly available equipment (a thermal evaporator). Recipes are also provided so that films with optimal optical properties can be routinely obtained.ISSN:2330-402

Resultats du benchmark CEA sur le serveur CDC 4680

SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : RP 10766 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

A customizable class of colloidal-quantum-dot spasers and plasmonic amplifiers

Colloidal quantum dots are robust, efficient, and tunable emitters now used in lighting, displays, and lasers. Consequently, when the spaser—a laser-like source of high-intensity, narrow-band surface plasmons—was first proposed, quantum dots were specified as the ideal plasmonic gain medium for overcoming the significant intrinsic losses of plasmons. Many subsequent spasers, however, have required a single material to simultaneously provide gain and define the plasmonic cavity, a design unable to accommodate quantum dots and other colloidal nanomaterials. In addition, these and other designs have been ill suited for integration with other elements in a larger plasmonic circuit, limiting their use. We develop a more open architecture that decouples the gain medium from the cavity, leading to a versatile class of quantum dot–based spasers that allow controlled generation, extraction, and manipulation of plasmons. We first create aberration-corrected plasmonic cavities with high quality factors at desired locations on an ultrasmooth silver substrate. We then incorporate quantum dots into These cavities via electrohydrodynamic printing or drop-casting. Photoexcitation under ambient conditions generates monochromatic plasmons (0.65-nm linewidth at 630 nm, Q ~ 1000) above threshold. This signal is extracted, directed through an integrated amplifier, and focused at a nearby nanoscale tip, generating intense electromagnetic fields. More generally, our device platform can be straightforwardly deployed at different wavelengths, size scales, and geometries on large-area plasmonic chips for fundamental studies and applications.ISSN:2375-254

Defect-Tolerant Plasmonic Elliptical Resonators for Long-Range Energy Transfer

ISSN:1936-0851ISSN:1936-086

Wedge Waveguides and Resonators for Quantum Plasmonics

Plasmonic structures can provide deep-subwavelength electromagnetic fields that are useful for enhancing light–matter interactions. However, because these localized modes are also dissipative, structures that offer the best compromise between field confinement and loss have been sought. Metallic wedge waveguides were initially identified as an ideal candidate but have been largely abandoned because to date their experimental performance has been limited. We combine state-of-the-art metallic wedges with integrated reflectors and precisely placed colloidal quantum dots (down to the single-emitter level) and demonstrate quantum-plasmonic waveguides and resonators with performance approaching theoretical limits. By exploiting a nearly 10-fold improvement in wedge-plasmon propagation (19 μm at a vacuum wavelength, λvac, of 630 nm), efficient reflectors (93%), and effective coupling (estimated to be >70%) to highly emissive (∼90%) quantum dots, we obtain Ag plasmonic resonators at visible wavelengths with quality factors approaching 200 (3.3 nm line widths). As our structures offer modal volumes down to ∼0.004λvac3 in an exposed single-mode waveguide–resonator geometry, they provide advantages over both traditional photonic microcavities and localized-plasmonic resonators for enhancing light–matter interactions. Our results confirm the promise of wedges for creating plasmonic devices and for studying coherent quantum-plasmonic effects such as long-distance plasmon-mediated entanglement and strong plasmon–matter coupling.ISSN:1530-6984ISSN:1530-699

Defect-Tolerant Plasmonic Elliptical Resonators for Long-Range Energy Transfer

Energy transfer allows energy to be moved from one quantum emitter to another. If this process follows the Förster mechanism, efficient transfer requires the emitters to be extremely close (<10 nm). To increase the transfer range, nanophotonic structures have been explored for photon- or plasmon-mediated energy transfer. Here, we fabricate high-quality silver plasmonic resonators to examine long-distance plasmon-mediated energy transfer. Specifically, we design elliptical resonators that allow energy transfer between the foci, which are separated by up to 10 μm. The geometry of the ellipse guarantees that all plasmons emitted from one focus are collected and channeled through different paths to the other focus. Thus, energy can be transferred even if a micrometer-sized defect obstructs the direct path between the focal points. We characterize the spectral and spatial profiles of the resonator modes and show that these can be used to transfer energy between green- and red-emitting colloidal quantum dots printed with subwavelength accuracy using electrohydrodynamic nanodripping. Rate-equation modeling of the time-resolved fluorescence from the quantum dots further confirms the long-distance energy transfer

Confocal reference free traction force microscopy

The mechanical wiring between cells and their surroundings is fundamental to the regulation of complex biological processes during tissue development, repair or pathology. Traction force microscopy (TFM) enables determination of the actuating forces. Despite progress, important limitations with intrusion effects in low resolution 2D pillar-based methods or disruptive intermediate steps of cell removal and substrate relaxation in high-resolution continuum TFM methods need to be overcome. Here we introduce a novel method allowing a one-shot (live) acquisition of continuous in- and out-of-plane traction fields with high sensitivity. The method is based on electrohydrodynamic nanodrip-printing of quantum dots into confocal monocrystalline arrays, rendering individually identifiable point light sources on compliant substrates. We demonstrate the undisrupted reference-free acquisition and quantification of high-resolution continuous force fields, and the simultaneous capability of this method to correlatively overlap traction forces with spatial localization of proteins revealed using immunofluorescence methods.ISSN:2041-172

Defect-Tolerant Plasmonic Elliptical Resonators for Long-Range Energy Transfer

Energy transfer allows energy to be moved from one quantum emitter to another. If this process follows the Förster mechanism, efficient transfer requires the emitters to be extremely close (<10 nm). To increase the transfer range, nanophotonic structures have been explored for photon- or plasmon-mediated energy transfer. Here, we fabricate high-quality silver plasmonic resonators to examine long-distance plasmon-mediated energy transfer. Specifically, we design elliptical resonators that allow energy transfer between the foci, which are separated by up to 10 μm. The geometry of the ellipse guarantees that all plasmons emitted from one focus are collected and channeled through different paths to the other focus. Thus, energy can be transferred even if a micrometer-sized defect obstructs the direct path between the focal points. We characterize the spectral and spatial profiles of the resonator modes and show that these can be used to transfer energy between green- and red-emitting colloidal quantum dots printed with subwavelength accuracy using electrohydrodynamic nanodripping. Rate-equation modeling of the time-resolved fluorescence from the quantum dots further confirms the long-distance energy transfer