Cylindrical vector beams of light from an electrically excited plasmonic lens

International audienceThe production of cylindrical vector beams from a low-energy, electric, microscale light source is demonstrated both experimentally and theoretically. This is achieved by combining a “plasmonic lens” with the ability to locally and electrically excite propagating surface plasmons on gold films. The plasmonic lens consists of concentric circular subwavelength slits that are etched in a thick gold film. The local excitation arises from the inelastic tunneling of electrons from the tip of a scanning tunneling microscope. We report on the emission of radially polarized beams with an angular divergence of less than ±4°

The influence of methotrexate-related transporter and metabolizing enzyme gene polymorphisms on peri-engraftment syndrome and graft-versus-host disease after haplo-hematopoietic stem cell transplantation in pediatric patients with malignant hematological diseases

BackgroundMethotrexate (MTX), utilized as a graft-versus-host disease (GvHD) prophylactic agent in allogeneic hematopoietic stem cell transplantation (allo-HSCT), has been proven to effectively decrease the occurrence of the peri-engraftment syndrome (Peri-ES) and acute GvHD (aGvHD). Changes in the pharmacodynamics of MTX are closely associated with gene polymorphisms in genes encoding drug-metabolizing enzymes and transporters. Nevertheless, the current studies mainly concentrate on leukemia or autoimmune diseases, and limited studies on allo-HSCT were reported.MethodsHere, we retrospectively assessed the relationship between MTX-related transporter and metabolizing enzyme gene polymorphisms, clinical characteristics, and outcomes in 57 pediatric patients who received haploid HSCT (haplo-HSCT) with malignant tumors at a single center.ResultsWe discovered all gene polymorphisms were in the Hardy–Weinberg equilibrium in our cohort. We discovered a significant correlation between platelet recovery time and ABCB1 (1236C>T) (p = 0.042). Compared with patients with SLCO1B1 (1865+4846T>C) TT, patients with SLCO1B1 (1865+4846T>C) TC/CC had an increased incidence of Peri-ES (p = 0.030). Based on the multivariate Cox analysis, we discovered that SLCO1B1 (1865+4846T>C) TT genotype was an independent protective factor for Peri-ES morbidity (hazard ratio (HR) = 0.464, p = 0.031), and the dose of mononuclear cells reinfused was significantly correlated with II–IV aGvHD (HR = 2.604, p = 0.039).ConclusionIn summary, our findings prove that the host’s genotypes might modify the risk of developing Peri-ES, contribute to a better understanding of the inter-individual difference in efficacy, and facilitate the development of individualized approaches to GvHD prophylaxis

Nanostructures plasmoniques pour le contrôle de l'émission de lumière excitée électriquement

In this thesis, we use different plasmonic nanostructures to control the emission of electrically-excited light. Our electrical emission is from an “STM-nanosource” which uses the inelastic tunnel current between the tip of a scanning tunneling microscope (STM) and a metallic sample, to locally excite both localized and propagating surface plasmon polaritons. The interaction of our STM-nanosource and a circular plasmonic lens (a series of concentric slits etched in a thick gold film) produces a radially polarized microsource of low angular spread (≈±4°). The influence of the structural parameters on the angular spread of the resulting microsource is also investigated. In addition, a low angular spread (<±7°) for a large wavelength range (650-850 nm) is achieved. Thus this electrically-driven microsource of nearly collimated light has a broad spectral response and is optimal over a wide energy range, especially in comparison with other resonant plasmonic structures such as Yagi-Uda nanoantennas. The interaction of our STM-nanosource and an elliptical plasmonic lens (a single elliptical slit etched in a thick gold film) is also studied. When the STM excitation is located at the focal point position of the elliptical plasmonic lens, a directional light beam of low angular spread is acquired. Moreover, in the experiment we find that by changing the eccentricity of the elliptical plasmonic lens, the emission angle is varied. It is found that the larger the eccentricity of the elliptical lens, the higher the emission angle. This study provides a better understanding of how plasmonic nanostructures shape the emission of light. The interaction of STM-excited SPPs and a planar plasmonic multi-layer stack structure is also investigated. It is demonstrated that using STM excitation we can probe the optical band structure of the Au-SiO₂-Au stack. We find that the thickness of the dielectric plays an important role in changing the coupling between the modes. We also compare the results obtained by both laser and STM excitation of the same stack structure. The results indicate that the STM technique is superior in sensitivity. These findings highlight the potential of the STM as a sensitive optical nanoscopic technique to probe the optical bands of plasmonic nanostructures. Finally, the interaction of an STM-nanosource and an individual triangular plate is also studied. We find that when the STM excitation is centered on the triangular plate, there is no directional light emission. However, when the STM-nanosource is located on the edge of the triangle, directional light emission is obtained. This study provides us a novel avenue to achieve directional light emission. We also study probing the optical LDOS of the triangle with the STM-nanosource. Thus, our results show that the manipulation of light is achieved through SPP-matter interactions. Using plasmonic nanostructures, we control the collimation, polarization, and direction of the light originating from the STM-nanosource.Dans cette thèse, nous utilisons différentes nanostructures plasmoniques pour contrôler l'émission de lumière excitée électriquement. Notre émission électrique provient d'une "nanosource STM" qui utilise le courant tunnel inélastique entre la pointe d'un microscope à effet tunnel (STM) et un échantillon métallique, pour exciter localement les plasmons polaritons de surface localisés et propagatifs. L’interaction de notre nanosource STM et d'une lentille plasmonique circulaire (une série de fentes concentriques gravées dans un film d'or épais) produit une microsource radialement polarisée de faible dispersion angulaire (≈ ± 4 °). L'influence des paramètres structuraux sur la propagation angulaire de la microsource résultante est également étudiée. En outre, une faible dispersion angulaire (<± 7 °) pour une grande plage de longueurs d'onde (650-850 nm) est obtenue. Ainsi, cette microsource électrique de lumière presque collimatée a une réponse spectrale large et est optimale sur une large plage d'énergie, en particulier en comparaison avec d'autres structures plasmoniques résonantes telles que les nanoantennes Yagi-Uda. L'interaction de notre nanosource STM et d'une lentille plasmonique elliptique (une seule fente elliptique gravée dans un film d'or épais) est également étudiée. Lorsque l'excitation STM est située au point focal de la lentille plasmonique elliptique, un faisceau lumineux directionnel à faible divergence est acquis. De plus, expérimentalement, nous trouvons qu'en changeant l'excentricité de la lentille plasmique elliptique, l'angle d'émission varie. On constate que plus l'excentricité de la lentille elliptique est grande, plus l'angle d'émission est élevé. Cette étude permet de mieux comprendre comment les nanostructures plasmoniques façonnent l'émission de lumière. L'interaction de SPP excités par STM et d'une structure de pile multicouche planaire plasmonique est également étudiée. Il est démontré qu'en utilisant l'excitation STM, nous pouvons sonder la structure de bande optique de la pile Au-SiO₂-Au. Nous trouvons que l'épaisseur du diélectrique joue un rôle important dans la modification du couplage entre les modes. Nous comparons également les résultats obtenus par excitation laser et STM de la même structure de pile. Les résultats indiquent que la technique STM est supérieure en sensibilité. Ces résultats mettent en évidence le potentiel de la STM en tant que technique de nanoscopie optique sensible pour sonder les bandes optiques des nanostructures plasmoniques. Enfin, l'interaction d'une nanosource STM et d'une plaque triangulaire individuelle est également étudiée. Nous trouvons que lorsque l'excitation STM est centrée sur la plaque triangulaire, il n'y a pas d'émission de lumière directionnelle. Cependant, lorsque la nanosource STM est située sur le bord du triangle, on obtient une émission de lumière directionnelle. Cette étude nous fournit une nouvelle voie pour atteindre l'émission de lumière directionnelle. Nous étudions également l'exploration du LDOS optique du triangle avec la nanosource STM. Ainsi, nos résultats montrent que la manipulation de la lumière est réalisée par des interactions SPP-matière. En utilisant des nanostructures plasmoniques, nous contrôlons la collimation, la polarisation et la direction de la lumière provenant de la nanosource STM

The mechanism of light emission from a scanning tunnelling microscope operating in air

International audienceThe scanning tunnelling microscope (STM) may be used as a low-energy, electrical nanosource of surface plasmon polaritons and light. In this article, we demonstrate that the optimum mode of operation of the STM for maximum photon emission is completely different in air than in vacuum. To this end, we investigate the emission of photons, the variation in the relative tip-sample distance and the measured current as a function of time for an STM operating in air. Contrary to the case of an STM operating in vacuum, the measured current between the tip and sample for an STM in air is very unstable (rapidly fluctuating in time) when the applied voltage between the tip and sample is in the ∼1.5–3 V range (i.e., in the energy range of visible photons). The photon emission occurs in short (50 μs) bursts when the STM tip is closest to the sample. The current instabilities are shown to be a key ingredient for producing intense light emission from an STM operating in air (photon emission rate several orders of magnitude higher than for stable current). These results are explained in terms of the interplay between the tunnel current and the electrochemical current in the ubiquitous thin water layer that exists when working in air

An electrical probe of the optical band structure in a plasmonic multilayer stack

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Surface plasmon polariton beams from an electrically excited plasmonic crystal

International audienceSurface plasmon polariton (SPP) beams with an in-plane angular spread of 8 degrees are produced by electrically exciting a 2D plasmonic crystal using a scanning tunneling microscope (STM). The plasmonic crystal consists of a gold nanoparticle (NP) array on a thin gold film on a glass substrate and it is the inelastic tunnel electrons (IET) from the STM that provide a localized and spectrally broadband SPP source. Surface waves on the gold film are shown to be essential for the coupling of the local, electrical excitation to the extended NP array, thus leading to the creation of SPP beams. A simple model of the scattering of SPPs by the array is used to explain the origin and direction of the generated SPP beams under certain conditions. In order to take into account the broadband spectrum of the source, calculations realized using finite-difference time-domain (FDTD) methods are obtained, showing that bandgaps for SPP propagation exist for certain wavelengths and indicating how changing the pitch of the NP array may enhance the SPP beaming effect. (C) 2016 Optical Society of Americ

Using a plasmonic lens to control the emission of electrically excited light

International audienceA local, low-energy, electrical method for the excitation of localized and propagating surface plasmon polaritons (SPPs) is attractive for both fundamental and applied research. In particular, such a method produces no excitation background light and may be integrated with nanoelectronics. Here we report on the electrical excitation of SPPs through the inelastic tunneling of low-energy electrons from the tip of a scanning tunneling microscope (STM) to the surface of a two-dimensional plasmonic lens. The plasmonic structure is a series of concentric circular slits etched in a thick gold film on a glass substrate. An outgoing circular SPP wave is generated from the tip-sample junction and is scattered into light by the slits. We compare the resulting emission pattern to that observed when exciting SPPs on a thin, unstructured gold film. For optimized parameters, the light emitted from the plasmonic lens is radially polarized. We describe the effects of the slit period and number, and lens diameter on the emission pattern and we diskuss how the light beam of low divergence is formed

An electrical probe of the optical band structure in a plasmonic multilayer stack

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Light beams in designed directions from electrically driven elliptical slit antennas

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Directional light beams by design from electrically driven elliptical slit antennas

International audienceWe report on the low-energy, electrical generation of light beams in specific directions from planar elliptical microstructures. The emission direction of the beam is determined by the microstructure eccentricity. A very simple, broadband, optical antenna design is used, which consists of a single elliptical slit etched into a gold film. The light beam source is driven by an electrical nanosource of surface plasmon polaritons (SPP) that is located at one focus of the ellipse. In this study, SPPs are generated through inelastic electron tunneling between a gold surface and the tip of a scanning tunneling microscope