This thesis presents a route towards a single photon source based on erbium-doped nanocrystals, fabricated with methods that use double nanohole optical tweezers. Single photon sources are an exciting quantum technology and erbium is good candidate as it emits in the low-loss fiber optic C-band, but it is a weak emitter. Double nanohole apertures can be designed with plasmonic resonances to enhance the local electric field. In this thesis, double nanohole optical tweezers are used to isolate and enhance the emission of erbium-doped nanocrystals, with the tuned geometry showing a factor of 50 additional enhancement over rectangular apertures. With the enhanced emission, nanocrystals with discrete levels of erbium emitters are detected and isolated in real-time, based on their level of emission. This real-time process demonstrates a major improvement over typical post-processing approaches. A novel method to anchor nanocrystals in a double nanohole using a photochemical thiol reaction was investigated which yielded 40% of nanoparticles anchoring within 2 μm of the DNH, with 5% inside. This is useful as otherwise the trapping laser must be maintained to keep the nanocrystal in the trap. Another challenge is coupling to an optical fiber, for which a method to combine trapping and coupling was explored. Colloidal pattern transfer is presented as a low-cost fabrication method for nanoaperture optical fiber tweezers, with fiber-based trapping demonstrated using 40 nm polystyrene nanospheres and hexagonal boron nitride. The preliminary results from these methods show great potential, and with further refinement they may lead towards a method to fabricate a low-cost fiber-coupled single photon source based on erbium-doped nanocrystals. / Graduate

This thesis presents the optical trapping of various nanometric particles (both biological and non-biological) and methods that can be used to extract information about the trapped particle from the signal transmitted through a nanoaperture trap. These methods are used to detect the excitation of vibrational modes in trapped particles due to the presence of a beat signal between two tunable trapping lasers and the molecular weight of the particle by examining the transmitted signal. Optical trapping has long been used to trap ever smaller particles in gentle non-destructive ways. In its infancy, only the optical trapping of micron sized particles was feasible. Due to various limitations, changes to the optical trapping scheme were needed to push its limits into the nanometric regime. Nanoaperture assisted optical trapping has allowed for the optical trapping of particles as small as 5 nm in diameter. By making use of specially chosen nanoapertures in gold films higher trapping strengths with lower incident laser powers have become possible. While this is an accomplishment in and of itself there are several issues associated with working with such small systems. Most notably, the ability to observe such systems is very limited. Traditional optical trapping of micron sized particles could make easy use of optical inspection, however in the nanometric regime this is not possible. It has since become a focus of the trapping community to find sophisticated ways to use the limited data available to probe these systems and their trapped targets. Once a particle is trapped the only information available about the particle is contained in the signal transmitted through the nanoaperture. The first main area of research in this thesis covers using this information to extract the molecular weight of the trapped particles for identification. In the same vein, Raman has been a tool widely used in the past to identify and probe systems of large ensembles of particles. While this is incredibly effective in some situations, it is not effective at the single particle limit. To form an analog that can be used within an optical trapping setup a new method of exciting Raman active vibrational modes with twin trapping lasers is presented. The low wavenumber vibrational spectra are presented for several different particles as well as a wide array of globular proteins. / Graduate

Cette thèse constitue un ensemble de travaux et de réflexions sur la question de la modélisation d’expériences en nano-optique utilisant la méthode des différences finies dans le domaine fréquentiel (FDFD) et la méthode des différences finies dans le domaine temporel (FDTD). D’abord, un code FDFD bidimensionnel, dédié au calcul de modes propres de guides d’ondes optiques, a été mis en œuvre et testé à travers une comparaison avec des résultats publiés. Dans une deuxième grande partie, nous étudions le piégeage optique de petites particules (de taille microscopique) à l’aide d’une antenne à nano-ouverture papillon (BNA) gravée à l’extrémité d’une sonde de microscope optique métallisée. Le confinement de lumière obtenue à la résonance de la nano-antenne permet un piégeage 3-D des nanoparticules de latex. Une étude systématique a été menée pour quantifier la puissance de la lumière incidente nécessaire pour un piégeage stable. Un bon accord entre les résultats expérimentaux et numériques a été obtenu dans le cas d’une BNA opérant dans l’eau à _ = 1064 nm pour le piégeage de particules de latex de 250 nm de rayon. En outre, les résultats numériques pour de plus petites particules sont présentés et montrent qu’une telle configuration est capable de piéger des particules avec des rayons aussi petits que 30 nm. Troisièmement, nous avons étudié le processus de piégeage optique basé sur l’amélioration du confinement, non seulement du champ électrique comme dans le cas de la BNA, mais aussi du magnétique que peut exhiber l’antenne métallique type diabolo (DA). Cette dernière a été récemment proposée car elle présente une résonance avec un fort confinement magnétique. Nous avons amélioré le design afin qu’une double résonance, électrique et magnétique, ait lieu au centre de la nano-antenne. Ce double confinement a ensuite été exploité pour exalter le gradient de champ au voisinage de l’antenne et ainsi aboutir à de meilleures efficacités de piégeage (moindre puissance). De plus, les résultats des simulations montrent que le processus de piégeage dépend fortement des dimensions des particules et que, pour des géométries particulières, un piégeage sans contact peut être réalisé. Cette structure doublement résonnante ouvre la voie à la conception d’une nouvelle génération de nano-pinces optiques à forte efficacit / This thesis is a set of work and reflections on modeling the experiments in nano-optics by using the finite difference method in the frequency domain (FDFD), and in time domain (FDTD). First, a two-dimensional code FDFD, dedicated to the calculation the eigenmodes of optical waveguides, has been implemented and tested through a comparison with results found in the literature. In a second large part, we study the optical trapping of small particles (of microscopic size) by using a bowtie nanoaperture antenna (BNA) engraved at the end of a metal-coated near-field optical microscope tip. The confinement of light obtained at the resonance of the nano-antenna allows 3-D trapping of latex nanoparticles. A systematic study was conducted to quantify the power of incident light necessary for stable trapping. Good agreement between the experimental and numerical results was obtained in the case of a BNA operating in water at _ = 1064 nm for the trapping of latex particles having a radius of 250 nm-radius. In addition, numerical results for smaller particles are presented and show that such configuration is capable of trapping particles with radii reaching 30 nm. Third, we studied the optical trapping process based on improved confinement of the electric field as in the case of the BNA, but also of the magnetic field, by using a metallic diabolo shape antenna (DA). This latter has been recently proposed because it exhibits resonance with a strong magnetic field confinement. We have improved the design in such a way that a double resonance, electric and magnetic, takes place in the center of the nano-antenna. This dual confinement was then used in order to enhance the field gradient in its vicinity and thus obtain better efficiencies of the trapping (less power). In addition, the simulation results show that the trapping process is greatly dependent of the particles size, and also show that, for specificl geometries, a trapping without contact can be achieved. This doubly resonant structure opens the way to the conception of a new generation of optical nano-tweezers with high efficiency.