Enhancing Magnetic Light Emission with All-Dielectric Optical Nanoantennas

Electric and magnetic optical fields carry the same amount of energy. Nevertheless, the efficiency with which matter interacts with electric optical fields is commonly accepted to be at least 4 orders of magnitude higher than with magnetic optical fields. Here, we experimentally demonstrate that properly designed photonic nanoantennas can selectively manipulate the magnetic versus electric emission of luminescent nanocrystals. In particular, we show selective enhancement of magnetic emission from trivalent europium-doped nanoparticles in the vicinity of a nanoantenna tailored to exhibit a magnetic resonance. Specifically, by controlling the spatial coupling between emitters and an individual nanoresonator located at the edge of a near field optical scanning tip, we record with nanoscale precision local distributions of both magnetic and electric radiative local densities of states (LDOS). The map of the radiative LDOS reveals the modification of both the magnetic and electric quantum environments induced by the presence of the nanoantenna. This manipulation and enhancement of magnetic light-matter interaction by means of nanoantennas opens up new possibilities for the research fields of opto-electronics, chiral optics, nonlinear&nano-optics, spintronics and metamaterials, amongst others.Peer ReviewedPostprint (author's final draft

SISTEMA DE RECONOCIMIENTO DE DÍGITOS MANUSCRITOS UTILIZANDO REDES NEURONALES

El reconocimiento de dígitos manuscritos es un entorno en creciente uso y por consiguiente requiere ir abordando alternativas para su implementación, el  uso de redes neuronales ha venido retomando el auge dentro del área de reconocimiento de patrones. Este documento muestra el uso de redes neuronales, a través de un software personalizado, como el motor detrás un sistema de reconocimiento de caracteres ópticos. En este sistema los dígitos numéricos son simplificados a través de filtros de imagen y luego presentados como entrada a la red neuronal para entrenarla (usando el algoritmo de retro-propagación) y ser capaz de clasificar otras muestras en la etapa de pruebas. Los resultados muestran tasas de reconocimiento cercanas al 85%, que se pueden considerar como aceptables para topologías de una sola capa, dejando pendiente para futuros experimentos el trabajo con redes multicapa pre-entrenadas, ya que suelen incrementar fuertemente su eficiencia

Parámetros de estabilidad en híbridos de girasol con alto contenido de oléico/Stability parameters in sunower hybrids with high oleic content

Se evaluaron híbridos de girasol que tienen aceite con alto contenido de ácido oléico, los cuales fueron Olisun 1, Olisun 2, Sabritas 1, Híbrido 1, Híbrido 2 e Híbrido 3, en los ambientes de Venecia, Durango, Durango, Durango en el ciclo Primavera-Verano 2010; y Venecia, Durango, en el ciclo Primavera-Verano 2011, bajo un diseño de bloques completos al azar con cuatro repeticiones. El análisis de parámetros de estabilidad, reveló diferencias signicativas (p < 0.05) entre híbridos para el contenido de ácido oléico. Para rendimiento de grano el híbrido 1 fue superior (p < 0.05) a los otros híbridos evaluados. El modelo de Eberhart y Russell para las variables ácido oléico y rendimiento clasicó a los híbridos como estables, con excepción del híbrido Sabritas 1 que tuvo desviación de la regresión signicativa que lo clasicó como inconsistente. Con base en el contenido de ácido oléico, rendimiento de grano y estabilidad, los mejores híbridos fueron Híbrido 3 y Sabritas 1

Monitorización de estructuras de concreto por fibras ópticas

Monitorización de estructuras de concreto por fibras óptica

Fabrication et caractérisation d'antennes patch plasmoniques

In this thesis, we exploit light-matter interaction between a single semiconductor CdSe/CdS nanocrystal and a plasmonic patch antenna. This work can be divided in two main parts. We have first characterized the photoluminescence dynamics and spectroscopic signatures of single nanocrystals at different excitation powers. High quality CdSe/CdS nanocrystals are single-photon sources at room temperature. Nevertheless, multiexcitonic emission occurs when two or more excitons are recombining radiatively. We have developed an analytical model which describes the number of photons emitted by a nanocrystal as a function of the mean number of excitons created in one excitation pulse. With this model, we can calculate the quantum efficiency of the bi-exciton recombination. The second part is devoted to the development and optimization of an optical lithography protocol for patch antennas. We have stablished a protocol that allows us to couple a thin Au nano-disk above a single nanocrystal in a deterministic way. We have first fabricated passive nanoantennas in order to study reflectivity spectroscopic properties in the plasmonic structure. Later on, we have fabricated several active patch nanoantennas coupled with single CdSe/CdS nanocrystals. We have demonstrated the acceleration of spontaneous emission thanks to the coupling with the plasmons nanodisk. For some antennas, we have evidenced a super-poissonian emission signature when a post-processing temporal filter is applied. Finally, we have evidenced the emission of light partially coherent of one antenna in the proximity of the metallic square edge.Nous étudions l'interaction lumière-matière d’un nanocristal CdSe/CdS individuel et une antenne patch plasmonique. Les études réalisées dans le cadre de ce travail peuvent être visualisées en deux parties. En première, nous avons caractérisé les propriétés de photoluminescence d'un nanocristal individuel en termes de la dynamique et la spectroscopie à différents conditions d’excitation. Les nanocristaux semi-conducteurs sont des sources de photon-unique à température ambiante. Néanmoins, l’émission multi-excitonique de ces émetteurs est possible lorsque la recombinaison de deux ou plus excitons devient radiative. Nous avons développé un modèle analytique qui permet de décrire le nombre de photons émis en fonction du nombre moyen d’excitons créés par une impulsion laser. Le modèle nous a permis d'estimer le rendement quantique de la transition bi-excitonique. La deuxième partie est consacrée à l'optimisation d’un protocole de fabrication d’antennes patch. Nous avons établi un protocole de lithographie optique qui permettre de coupler un nanodisque d’or avec un nanocristal individuel de manière déterministe. En première temps, nous avons fabriqué antennes passives afin d'analyser les propriétés de réflectivité de la structure, puis nous avons fabriqué des antennes couplées à une boite quantique. Nous avons montré la modification de l’émission spontanée due au couplage avec l’antenne. Nous avons mis en évidence une émission super-poissonnienne de l’antenne après un filtrage temporel, ainsi que l’émission de lumière partialement cohérente

Fabrication and characterization of plasmonic patch nanoantennas

Nous étudions l'interaction lumière-matière d’un nanocristal CdSe/CdS individuel et une antenne patch plasmonique. Les études réalisées dans le cadre de ce travail peuvent être visualisées en deux parties. En première, nous avons caractérisé les propriétés de photoluminescence d'un nanocristal individuel en termes de la dynamique et la spectroscopie à différents conditions d’excitation. Les nanocristaux semi-conducteurs sont des sources de photon-unique à température ambiante. Néanmoins, l’émission multi-excitonique de ces émetteurs est possible lorsque la recombinaison de deux ou plus excitons devient radiative. Nous avons développé un modèle analytique qui permet de décrire le nombre de photons émis en fonction du nombre moyen d’excitons créés par une impulsion laser. Le modèle nous a permis d'estimer le rendement quantique de la transition bi-excitonique. La deuxième partie est consacrée à l'optimisation d’un protocole de fabrication d’antennes patch. Nous avons établi un protocole de lithographie optique qui permettre de coupler un nanodisque d’or avec un nanocristal individuel de manière déterministe. En première temps, nous avons fabriqué antennes passives afin d'analyser les propriétés de réflectivité de la structure, puis nous avons fabriqué des antennes couplées à une boite quantique. Nous avons montré la modification de l’émission spontanée due au couplage avec l’antenne. Nous avons mis en évidence une émission super-poissonnienne de l’antenne après un filtrage temporel, ainsi que l’émission de lumière partialement cohérente.In this thesis, we exploit light-matter interaction between a single semiconductor CdSe/CdS nanocrystal and a plasmonic patch antenna. This work can be divided in two main parts. We have first characterized the photoluminescence dynamics and spectroscopic signatures of single nanocrystals at different excitation powers. High quality CdSe/CdS nanocrystals are single-photon sources at room temperature. Nevertheless, multiexcitonic emission occurs when two or more excitons are recombining radiatively. We have developed an analytical model which describes the number of photons emitted by a nanocrystal as a function of the mean number of excitons created in one excitation pulse. With this model, we can calculate the quantum efficiency of the bi-exciton recombination. The second part is devoted to the development and optimization of an optical lithography protocol for patch antennas. We have stablished a protocol that allows us to couple a thin Au nano-disk above a single nanocrystal in a deterministic way. We have first fabricated passive nanoantennas in order to study reflectivity spectroscopic properties in the plasmonic structure. Later on, we have fabricated several active patch nanoantennas coupled with single CdSe/CdS nanocrystals. We have demonstrated the acceleration of spontaneous emission thanks to the coupling with the plasmons nanodisk. For some antennas, we have evidenced a super-poissonian emission signature when a post-processing temporal filter is applied. Finally, we have evidenced the emission of light partially coherent of one antenna in the proximity of the metallic square edge

Differential reflectivity spectroscopy on single patch nanoantennas

International audienceWe present an experimental technique adapted to characterize individual metallic nanostructures in terms of differential reflectivity spectroscopy. We analyze gold patch nanoantennas holding different morphological properties. Our experimental methodology shows steady and reliable results consistent with classical analytical approximations and simulation methods. This technique allows us to identify absorption properties of metallic nanostructures commonly associated with surface plasmon resonances. By contrasting the light absorbed solely by the metallic antenna with respect to a surrounding reference medium, we found that some antennas show absorption of almost 50% of the incident light across the range of the visible spectrum. Plasmonic patch nanoantennas are promising systems in which the confinement of the electromagnetic field inside the dielectric gap strongly modifies the local density of states

Parámetros de estabilidad en híbridos de girasol con alto contenido de oleico

Sunflower hybrids that have oil with high oleic acid content (Olisun 1, Olisun 2, Sabritas 1, Hybrid 1, Hybrid 2 and Hybrid 3) were evaluated in the environments of Venecia, Durango and Durango, Durango in the 2010 Spring-Summer cycle, and in Venecia, Durango in the 2011 Spring-Summer cycle, under a randomized complete block design with four replicates. Analysis of stability parameters revealed significant differences (p<0.05) among hybrids for oleic acid content. For grain yield, hybrid 1 was superior (p<0.05) to the other hybrids evaluated. The Eberhart and Russell model for the variables oleic acid and yield classified the hybrids as stable, with the exception of the hybrid Sabritas 1 that had significant deviation of the regression that classified it as inconsistent. Based on oleic acid content, grain yield and stability, the best hybrids were Hybrid 3 and Sabritas 1.Se evaluaron híbridos de girasol que tienen aceite con alto contenido de ácido oléico, los cuales fueron Olisun 1, Olisun 2, Sabritas 1, Híbrido 1, Híbrido 2 e Híbrido 3, en los ambientes de Venecia, Durango, Durango, Durango en el ciclo Primavera-Verano 2010; y Venecia, Durango, en el ciclo Primavera-Verano 2011, bajo un diseño de bloques completos al azar con cuatro repeticiones. El análisis de parámetros de estabilidad, reveló diferencias significativas (p < 0.05) entre híbridos para el contenido de ácido oléico. Para rendimiento de grano el híbrido 1 fue superior (p < 0.05) a los otros híbridos evaluados. El modelo de Eberhart y Russell para las variables ácido oleico y rendimiento clasificó a los híbridos como estables, con excepción del híbrido Sabritas 1 que tuvo desviación de la regresión significativa que lo clasificó como inconsistente. Con base en el contenido de ácido oléico, rendimiento de grano y estabilidad, los mejores híbridos fueron Híbrido 3 y Sabritas 1

Enhancing Magnetic Light Emission with All-Dielectric Optical Nanoantennas

Electric and magnetic optical fields carry the same amount of energy. Nevertheless, the efficiency with which matter interacts with electric optical fields is commonly accepted to be at least 4 orders of magnitude higher than with magnetic optical fields. Here, we experimentally demonstrate that properly designed photonic nanoantennas can selectively manipulate the magnetic versus electric emission of luminescent nanocrystals. In particular, we show selective enhancement of magnetic emission from trivalent europium-doped nanoparticles in the vicinity of a nanoantenna tailored to exhibit a magnetic resonance. Specifically, by controlling the spatial coupling between emitters and an individual nanoresonator located at the edge of a near field optical scanning tip, we record with nanoscale precision local distributions of both magnetic and electric radiative local densities of states (LDOS). The map of the radiative LDOS reveals the modification of both the magnetic and electric quantum environments induced by the presence of the nanoantenna. This manipulation and enhancement of magnetic light-matter interaction by means of nanoantennas opens up new possibilities for the research fields of opto-electronics, chiral optics, nonlinear&nano-optics, spintronics and metamaterials, amongst others.Peer Reviewe