xx, 162 p. ; ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / In this thesis we theoretically and experimentally investigate the subwavelength manipulation of light with nano-scale patterned metallodielectric resonators. By coupling light to surface plasmon excitations, we calculate the modified dispersion relation of the resulting surface plasmon polariton (SPP) modes in two types of subwavelength resonators: (i) closed, spherical micro-resonators with nano-scale metal-dielectic-metal shells; (ii) periodic, metal-dielectric-metal-layered silica surfaces. We show theoretically that with the proper geometric parameters, one can use sub-wavelength structure on spherical surfaces to manipulate the SPP dispersion relation in a highly tunable fashion. A tunable avoided-crossing of plasmonic dispersion bands is found to be the result of the coherent near-field coupling of silver nano-shell SPP modes. By developing our own stable computational algorithms, we calculated the far-field scattering of these metal-dielectric-metal layered micro-resonators. We demonstrate that the near-field interaction of the SPPs leads to a tunable, SPP induced transparency in the composite particle's scattering and extinction cross-sections. Utilizing finite element calculations, periodically-modulated metal-dielectric-metal layers are shown to alter the transmission properties of plasmon enhanced transmission through their support of interior surface plasmon (ISP) modes. Our simulations indicate that, subwavelength silver-silica-silver trilayers coating arrays of silica cylinders support ISP modes analogous to those found in spherical metal-dielectric-metal shells. We examine the coupling between ISP and radiating SPPs, and find the possibility of efficient free-space coupling to ISP modes in planar geometries. Further, the excitation of these ISP modes is found to predicate plasmon enhanced transmission, adding directionality and refined frequency selection. Experimentally, we show that self-assembled monolayers of silica spheres form a novel substrate for tunable plasmonic surfaces. We have developed a deposition method to conformally coat these hexagonal-close-packed substrates with nano-scale silver-polystyrene-silver coatings. We use angle-resolved spectroscopy to study their transmission properties. We have discovered that the presence of the silver-polystyrene-silver layer supports the excitation of ISP modes, and that these excitations significantly alter the plasmon enhanced transmission. Finally, we have discovered that the use of the ordered monolayers as a plasmonic substrate can create a new effect in conjunction with plasmon enhanced transmission: directionally asymmetric transmission. This is demonstrated with optically thick silver coatings evaporated upon onto the ordered sphere monolayers. / Adviser: Miriam Deutsch

Nanoelectromechanical systems (NEMS) have drawn considerable attention towards several sensing applications such as force, spin, charge and mass. These devices due to their smaller size, operate at very high frequencies (MHz - GHz) and have very high quality factors (102 -105). However, the early onset of nonlinearity limits the linear dynamic range of these devices. In this work we investigate the nonlinearities and their effect on the performance of graphene based NEMS. Electromechanical devices based on 2D materials are extremely sensitive to strain. We studied the effect of strain on the performance of single layer Graphene NEMS and show how the strain in Graphene NEMS can be tuned to increase the range of linear operation. Electromechanical properties of the doubly clamped graphene resonators deviates from the flat rectangular plate as the former possesses geometrical imperfections which are sometimes orders of magnitude larger than the thickness of the resonator. Due to these imperfections we report an initial softening behavior, turning to strong hardening nonlinearity for larger vibration amplitude in the back-bone curve. We have also studied the frequency stability of graphene resonators. Frequency stability analysis indicates departure from the nominal frequency of the resonator with time. We have used Allan Variance as a tool to characterize the frequency stability of the device. Frequency stability of graphene resonator is studied in an open loop configuration as a function of temperature and bias voltage. The thesis concludes with a remark on the future work that can be carried out based on the present studies.

Le graphène et les nanotubes de carbone, assimilés à des nano-systèmes graphitiques, partagent des propriétés mécaniques, optiques, électroniques et vibrationnelles uniques. Associant faible masse, grande rigidité et comportement semi-transparent, des membranes de 10 à 100 couches de graphène ont été suspendues au dessus d'un substrat réfléchissant, formant ainsi un résonateur mécanique couplé à une cavité optique. Le projet de cette thèse repose sur les diffusions élastiques et inélastiques de la lumière pour sonder les contraintes mécaniques et les effets thermiques dans ces nano-systèmes graphitiques. Ce type de mesure repose sur la spectroscopie Raman, sensible aux phonons optiques du matériau sondé. Un premier aspect du présent projet de thèse porte sur l'utilisation de cavités optiques à base de graphène comme élément de base pour constituer un système hybride. Après avoir déposé une couche de molécules à la surface de ces membranes, nous avons montré que le signal Raman des molécules est exalté par un effet d'interférences optiques constructives. Nous avons mis en évidence la possibilité de moduler ce signal en se déplaçant le long de l'échantillon, ou en variant la position de la membrane à l'aide d'une actuation électrostatique. De plus, on peut observer des effets thermiques importants associés aux phénomènes d'interférences optiques dans ces membranes à base de graphène. Le second axe de cette thèse est la détection du mouvement et des contraintes mécaniques dans un résonateur graphitique (membranes de graphène multicouche, nanotubes, etc.). Au travers d'expériences menées sur des membranes suspendues de graphène multicouche, nous avons détecté la résonance mécanique de deux façons : en analysant la modulation de la lumière réfléchie et en mesurant les variations de la réponse Raman du résonateur. Cette détection, reposant sur l'augmentation des contraintes mécaniques à résonance, associe le mouvement mécanique du résonateur à un décalage en énergie des photons Raman et représente un schéma original de couplage optomécanique. / Graphitic nano systems, such as graphene or carbon nanotubes, share unique mechanical, optical, electrical and vibrational properties. Combining low mass, high rigidity and semi-transparent behavior, membranes made of 10 to 100 graphene layers have been suspended over a reflecting substrate. This results in a nanomechanical resonator coupled to an optical cavity. This Phd project is based on elastic and inelastic scattering of light in order to probe mechanical stress and thermal effects within graphitic nano systems. This type of measurement is made by Raman spectroscopy which is sensitive to optical phonons. A first part of this Phd project is about using graphene based optical cavities as a constitutive blocks to make a hybrid system. We have shown interferential enhancement of Raman signal of molecules grafted on the membrane surface. We have also demonstrated the possibility to tune this molecular Raman signal by moving along the suspended membrane, or by changing the membrane position using electrostatic actuation. Moreover, we have observed important thermal effects associated to optical interferences within these graphene based cantilevers. A second part of this Phd project is the detection of motion and mechanical stress within a graphitic nano resonator. Through experiments on suspended multilayer graphene membranes, we have detected the mechanical resonance by two different means : by analyzing the reflected light modulation, and by measuring the variations of the Raman signal of the resonator. This spectral detection, based on the increase of the mechanical stress at resonance, couples the mechanical motion of the resonator to a shift in energy of the Raman scattered photons. This represents an original scheme for optomechanical coupling.