Optical nanoantennas have raised much interest during the past decade for their vast potential in photonics applications. This thesis investigates the response of periodic arrays of nanomonopoles and nanodipoles on a silicon substrate, covered by water, to variations of antenna dimensions. These arrays are illuminated by a plane wave source located inside the silicon substrate. Modal analysis was performed and the mode in the nanoantennas was identified. By characterizing the properties of this mode certain response behaviours of the system were explained. Expressions are offered to predict approximately the resonant length of nanomonopoles and nanodipoles, by accounting for the fringing fields at the antenna ends and the effects of the gap in dipoles. These expressions enable one to predict the resonant length of nanomonopoles within 20% and nanodipoles within 10% error, which significantly facilitates the design of such antennas for specific applications.

Optical nanoantennas have raised much interest during the past decade for their vast potential in photonics applications. This thesis investigates the response of periodic arrays of nanomonopoles and nanodipoles on a silicon substrate, covered by water, to variations of antenna dimensions. These arrays are illuminated by a plane wave source located inside the silicon substrate. Modal analysis was performed and the mode in the nanoantennas was identified. By characterizing the properties of this mode certain response behaviours of the system were explained. Expressions are offered to predict approximately the resonant length of nanomonopoles and nanodipoles, by accounting for the fringing fields at the antenna ends and the effects of the gap in dipoles. These expressions enable one to predict the resonant length of nanomonopoles within 20% and nanodipoles within 10% error, which significantly facilitates the design of such antennas for specific applications.

Optical nanoantennas have raised much interest during the past decade for their vast potential in photonics applications. This thesis investigates the response of periodic arrays of nanomonopoles and nanodipoles on a silicon substrate, covered by water, to variations of antenna dimensions. These arrays are illuminated by a plane wave source located inside the silicon substrate. Modal analysis was performed and the mode in the nanoantennas was identified. By characterizing the properties of this mode certain response behaviours of the system were explained. Expressions are offered to predict approximately the resonant length of nanomonopoles and nanodipoles, by accounting for the fringing fields at the antenna ends and the effects of the gap in dipoles. These expressions enable one to predict the resonant length of nanomonopoles within 20% and nanodipoles within 10% error, which significantly facilitates the design of such antennas for specific applications.

Resonance structures have long been employed by RF and microwave devices ranging from antennas, to wave guides. These resonance structures have exhibited an enormous amount of control over the wavelength selectivity, polarization, and directivity of the electromagnetic radiation which couples to the structure. Traditional geometrical optics has alternatively used discrete optical components such as lenses, gratings, and polarizers to accomplish equivalent control over optical radiation. This dissertation contributes to the larger body of literature that applies lessons learned in RF and microwave resonance structures, to nanoscale resonance structures. Optoelectronic nanoscale resonance structures were fabricated and characterized using both experimental and numerical methods. Two nanoscale resonance structures were investigated: an antenna inspired Yagi-Uda array, and a metasurface inspired interdigitated structure. Experimental devices containing the nanoscale resonance structures were fabricated on semiconducting substrates forming metal-semiconductor-metal photodiodes. The spectral response of the nanoscale resonance photodiode was determined by measuring the photocurrent or photovoltage resulting from incident monochromatic light which was swept through wavelengths from 400 nm to 2000 nm. The previously mentioned Yagi-Uda based device exhibited two maxima in photoresponse at 1110 nm and 1690 nm. Effective wavelength scaling was applied to the Yagi-Uda nanoantenas, and consistency was demonstrated between the theoretical effective wavelength and experimental photoresponse maxima. The spectral response of the interdigitated structure demonstrated good qualitative agreement with the finite element modeled absorbance in an equivalent structure. Analysis of the modeled absorbance suggests that hot electron injection contributes to the photoresponse, and the spectral response of the detector device may be tuned by varying the geometrical parameters of the device. An optimized device was proposed that could improve photodetection efficiency using nanoscale resonance devices. Antenna inspired nanoscale resonance structures may be used to probe fundamental physical phenomena such as hot carrier generation, hot carrier transport, and surface plasmon resonances. Combined optical and electrical-optoelectronic devices exploiting these phenomena may be realized for a variety of applications, eliminating some or all of the discrete optical components required for optoelectronic systems and hence significantly reducing the SWaP cost of optoelectronic systems. / Doctor of Philosophy / Resonance structures have long been employed by RF and microwave devices ranging from antennas, to wave guides. These resonance structures have exhibited an enormous amount of control over radio waves. Traditional optics has alternatively used discrete components such as lenses, gratings, and polarizers to accomplish equivalent control over light waves. This dissertation contributes to the larger body of literature that applies lessons learned in RF and microwave resonance structures, to nanoscale resonance structures. Optoelectronic nanoscale resonance structures were fabricated and characterized using both experimental and computational methods. Two nanoscale resonance structures were investigated: an antenna inspired Yagi-Uda array, and a metasurface inspired interdigitated structure. The ability of both devices to detect light of a particular wavelength was then tested. The photoresponse of the device containing a Yagi-Uda array is consistent with RF Yagi-Uda antennas when considered in accordance with the concept of effective wavelength. The experimental response of the interdigitated structure demonstrated good qualitative agreement with the computational modeled absorbance in an equivalent structure. Analysis of the modeled absorbance suggests that the spectral response of the detector device may be tuned by varying the geometrical parameters of the device. An optimized device was proposed that could improve photodetection efficiency using nanoscale resonance devices. Antenna inspired nanoscale resonance structures may be used to probe fundamental physical phenomena such as hot carrier generation, hot carrier transport, and surface plasmon resonances. Combined optical and electrical-optoelectronic devices exploiting these phenomena may be realized for a variety of applications, eliminating some or all of the discrete optical components required for optoelectronic systems and hence significantly reducing the SWaP cost of optoelectronic systems.

Nanometallic structures efficiently convert light to surface plasmon-polaritons (SPPs) localized to ultra-small volumes. Such structures can provide highly enhanced fields and are of interest in applications involving plasmon-enhanced nonlinear optics. In this study, the devices consist of rectangular gold nanoantennas on a graphene layer on a SiO2/Si substrate. The nanoantennas are used to exploit SPPs to enhance the interaction between graphene and light. Specifically, plasmon-enhanced Raman scattering from graphene is of interest. Here, the nanoantennas are spectrally-aligned with a Stokes wavelength of graphene. With the addition of a second laser source, stimulated Raman scattering can be achieved. The first laser source pumps the sample’s atoms and molecules into virtual excited states and the second one stimulates emission of a photon and relaxation to a higher mode of the ground state. This work involves designing and constructing a stimulated and spontaneous Raman microscope and also a reflectance measurement tool. Within the framework of this thesis, Raman scattering enhancement in graphene based on plasmonic resonant enhancement of the Stokes emission is demonstrated, providing a maximum cross-sectional gain of approximately 500 per antenna. This work also shows the normalized reflectance response of the nanoantenna structures of different length and width and how their resonant wavelengths shift.

In this work full parametric analysis of nano antennas is presented. To begin with, optical or electronic properties of noble metals such as gold and copper were studied in details to get a clear understanding of their reaction to an incident electromagnetic wave. Complex frequency dependent dielectric functions indicated that in THz metals acts as a dielectric with significant absorption. Simultaneous optimization of the length and the bow angle of a bow-tie antenna resulted in relative electric field intensity enhancement of 8 orders of magnitude for 0.5nm gap and 4 orders of magnitude for 50nm around 28THz resonance frequency. These results are at least 2 orders of magnitude greater than the published optical antennas. Physical reasons behind field localization and intensity enhancement  are  discussed  in  details.  The  solution  of  Maxwell’s  equations  at   the  interface between metallic nano antenna and air is also present in this piece of research. The derived dispersion relation of surface plasmons shows momentum matching at 28.3 THz between free propagating electromagnetic fields’ modes in air and localized modes at the interface. Consequently, Propagating electromagnetic waves are ensured to couple to localized surface propagating modes producing filed enhancement. The integrated SiO2 matching section is theoretically proven to increase transmission to substrate to 75% (compared to 40% without it) which in turn improves the coupled power by 40 times. Nano antennas were fabricated in house using Electron beam lithography with a precise gap of 50nm. In addition, THz diode was designed, fabricated and integrated to the nano antennas to rectify the enhanced THz signal. The integration of the nano diode required a precise overlap of the two arms of the antenna in the rage of 100nm. In order to overcome two arms overlap fabrication challenges, three layer alignment technique was used to produce precise overlap.The THz rectifier was electrically tested and shown high sensitivity and rectification ability without any bias. Finally, nano antenna integrated diode is under optical testing using a 10.6μm Co2 laser at Electro-Optics Lab, Prince Sultan Advanced Technologies Research Institute (PSATRI), King Saud University due to the unavailability of the measurement setup in KAUST.

This thesis covers three different topics. The first part is a pedagogical review of the basic principles and recent advances in nonlinear optics. It was originally written as a chapter for the proceedings of the “International School of Physics (Enrico Fermi)” summer school on Photonics held in June, 2014. It is included to provide some background information about nonlinear optical processes in general, and is particularly relevant for the third part of this thesis which is based on the second-order nonlinear optical process of spontaneous parametric downconversion. The second part is based on original research, and deals with superradiance in plasmonic nanostructures. The process of superradiance, as introduced by Dicke in 1954, entails the shortening of the spontaneous emission lifetime of a collection of N quantum emitters as a consequence of the development of a macroscopic dipole moment. Specifically, the lifetime is shortened by a factor of 1/N, and the linewidth is broadened by a factor of N. Such a linewidth dependence has been previously observed in systems of several plasmonic ‘emitters’. However, a clear physical insight into this phenomenon and how it relates to Dicke superradiance has not been shown yet. In this part, we demonstrate by experiment, simulation, and a simple analytical model that Dicke’s superradiance can indeed be observed in a planar array of plasmonic nanoantennas, with a linewidth that scales linearly with the number of nanoantennas within a square wavelength. The third part is also based on original research, and is based on the scal- ing laws of spontaneous parametric downconversion (SPDC) for a type-I phase- matching configuration. The variation of bi-photon generation rate, heralding efficiency and radiance with parameters such as crystal length, pump focussing and collection waist sizes are examined for collinear and non-collinear emission. The results can be used to maximize the brightness of the SPDC source or increase the heralding efficiency depending on the application.

In this thesis, an approach for developing single-photon sources at the 1550nm wavelength will be demonstrated, based on optical trapping of luminescent upconverting nanoparticles. A single-photon source is a source that emits a single photon at a time, and hence it is a source of quantum bits that constitutes the basic building units in quantum computers and quantum communications. The approach exploits the plasmonic properties of gold films and the waveguiding characteristics of single mode optical fibers (SMFs). We start by planar nanofabrication of subwavelength nanoapertures in a thin gold film based on finite difference time domain simulations for a peak transmission at the wavelength in question. Subsequently, using ultraviolet curable epoxy adhesion material, a nanoaperture patterned on a gold film can be transferred to an SMF tip forming a nanoantenna enhanced optical fiber tweezer (NAFT). As a final step in building the optical tweezer, a test of the capability of the integrated optical fiber tweezer to trap 20 nm, and 30nm polystyrene nanospheres, as well as luminescent upconverting nanoparticles (UCNPs), has been experimentally realized with encouraging results. In addition to the optical trapping of the luminescent nanoparticles, the nano aperture antenna can improve light coupling into the low loss optical fiber guiding channel. Also, it could have a positive influence on enhancing the photon emission rate through the Purcell effect. Furthermore, we have combined NAFT with a low insertion loss wave splitter, a wavelength-division multiplexer (WDM), to allow measuring the 1550nm photon-emission statistics on a cooled superconducting nanowire single-photon detector (SNSPD) at ~ 2.4o K. Eventually, nanoantenna enhanced optical fiber tweezers can play an essential role in optical trapping towards developing single-photon sources and the emerging technology of quantum information processing, computation, and cryptography. / Graduate

Au cours des dernières années, la communauté scientifique s'est intéressée de plus en plus à l'acquisition de sources d'énergie renouvelables vertes et propres par rapport aux combustibles fossiles traditionnels. Le rayonnement solaire est une source particulièrement abondante d'énergie renouvelable qui a été largement utilisée dans les véhicules, les machines et les bâtiments, entre autres. Il y a généralement deux manières différentes d'utiliser l'énergie solaire: la chaleur et l'électricité. La principale motivation de ce travail de thèse est d'utiliser cette abondante source d'énergie pour produire une petite fraction de la tension et du courant continu de sortie. Puisque le spectre solaire se situe dans les longueurs d'onde à l'échelle nanométrique ou dans la bande térahertz, les antennes optiques seront utilisées comme une nouvelle technologie de nanotechnologie pour capter et récolter l'énergie solaire. Les antennes optiques ont des propriétés similaires à celles de leurs homologues micro-ondes, mais leur avantage réside dans des moyens sans précédent pour adapter les champs électromagnétiques dans tous leurs aspects et applications. Par conséquent, avec les détails mentionnés ci-dessus, l'idée principale de cette thèse est de capturer le rayonnement infrarouge solaire et l'utiliser pour produire une tension continue de sortie. La première partie de cette thèse est consacrée à la compréhension du fonctionnement de la collecte d'énergie par radiofréquence (RF) et à la présentation d'un concept de rectenna. La deuxième partie traite de l'introduction et de la simulation d'antennes optiques à base de résonateurs diélectriques (DR) car elles offrent moins de pertes à la bande THz. Deux conceptions de DR différentes sont proposées fonctionnant à la fréquence centrale de 193,5 THz (longueur d'onde 1550 nm). La troisième partie traite de la contribution principale à ce travail en termes de conception, simulation et fabrication d'une antenne optique Yagi-uda à haut gain et large bande. La technique de lithographie par faisceau d'électrons est utilisée pour réaliser la structure proposée. En dehors de la conception de l'élément unique Yagi-uda, diverses configurations de réseau ont été simulées avec la réalisation d'un réseau d'éléments 100 x 100 fabriqué sur un substrat de silicium. Pour produire une certaine quantité de tension de sortie, deux techniques ont été utilisées pour tester le réseau d'antennes optiques Yagi-uda. La première technique impliquait l'intégration du réseau Yagi-uda avec une diode fermionique du commerce qui produisait une tension de sortie de 0,15 V par excitation à partir d'une lumière visible et de 0,52 V par excitation directe à partir d'un laser à 1550 nm. La deuxième technique est basée sur la dissipation thermique entre des métaux dissemblables produisant une tension de sortie. Quatre lasers à longueurs d'onde différents (532 nm, 650 nm, 940 nm et 1550 nm) ont excité trois conceptions de nantenna réalisées. Parmi ces conceptions, la tension de sortie maximale de 0,82 V a été produite par le réseau Yagi-uda lorsqu'il est excité via un laser de 1550 nm. / Recent years have witnessed an increased interest by the scientific community to acquire green and clean renewable sources of energy compared to traditional fossil fuels. Solar radiation is one particular abundant source of renewable energy that has been widely applied in vehicles, machines, and buildings, among others. There are generally two different ways in which solar energy is used – heat and electricity. The main motivation of this thesis work is to utilize that abundant source of energy in producing a small fraction of output DC voltage and current. Since the solar spectrum lies in the nano scale wavelengths or terahertz band, optical antennas as a novel nano fabrication technology will be used to capture and harvest the solar energy. Optical antennas have properties similar to their microwave counterparts, but the advantage they have is in terms of unprecedented means to tailor electromagnetic fields in all its aspects and applications. Therefore, with the aforementioned details, the main idea of this thesis is to capture the solar infrared radiation and utilize it for producing output DC voltage. The first part of this thesis is dedicated to understanding the working of radio frequency (RF) energy harvesting and presenting a rectenna design. The second part deals with the introduction and simulation of optical antennas based of dielectric resonators (DR) as they offer fewer losses at the THz band. Two different DR designs are proposed working at the center frequency of 193.5 THz (1550 nm wavelength). The third part discusses the main contribution to this work in terms of design, simulation and fabrication of a high gain and wideband Yagi-uda optical antenna. E-beam lithography technique is used to realize the proposed structure. Apart for the single element Yagi-uda design, various array configurations have been simulated with realization of a 100 x 100 elements array fabricated on a silicon substrate. To produce a certain amount of output voltage, two techniques were deployed in testing the realized Yagi-uda optical antenna array. The first technique involved integration of the Yagi-uda array with a commercial fermionic diode that produced output voltage of 0.15 V via excitation from a visible light and 0.52 V with direct excitation from a 1550 nm laser. The second technique is based on thermal dissipation among dissimilar metals producing an output voltage. Four different wavelength (532 nm, 650 nm, 940 nm and 1550 nm) lasers excited three realized nantenna designs. Among these designs, the maximum output voltage of 0.82 V was produced by the Yagi-uda array when excited via 1550 nm laser.

Dans ce travail de thèse, on s’intéresse aux applications des concepts d’antenne pour la manipulation de la lumière. Aux fréquences optiques, les antennes métalliques font intervenir des modes de surfaces dit plasmoniques permettant une forte interaction lumière/matière dans des volumes hautement confinés. Pour tirer partie de cette propriété, on s’intéressera à trois applications des antennes plasmoniques. D’abord dans le cadre des sources de photons uniques, on présentera une étude théorique et expérimentale des performances d’émetteurs uniques en présence d’une antenne planaire métallique. Nous proposerons ensuite une stratégie pour améliorer les performances de l’antenne. Puis dans le cadre de la génération électrique de lumière par effet tunnel inélastique, on analysera la modification des propriétés de rayonnement en présence d’un petit cylindre métallique. Cette analyse ouvre la voie à la conception de sources électriques intégrées de plasmons de surface. Enfin dans le cadre de la détection de molécules en faible quantité, on étudiera théoriquement l’interaction d’un faisceau infrarouge avec une couche de molécules résonnantes déposées sur un miroir métallique nanostructuré. / The work of this thesis has been devoted to a few applications of antenna concepts for the manipulation of light. In the optical range, surface modes called surface plasmon polaritons take place in the vicinity of metallic antennas, enabling a strong light/matter interaction within highly confined volumes. In order to take advantage of this property, three applications of plasmonic antennas will be investigated. First, in the case of single-photon sources, both theoretical and experimental studies of single-emitters performance when coupled to a planar metallic antenna will be presented. A strategy to enhance its performance will be studied theoretically. Then, in the case of electrical generation of light by inelastic electron tunneling, we will analyse the modification of radiation properties close to a metallic nano-rod. This analysis paves the way towards the design of integrated, compact electrical sources of surface plasmons. Finally, in the case of detecting a weak quantity of molecules, the interaction between an infrared light beam and a sub-nanometric layer of resonant molecules deposited on a nanostructured metallic mirror will be studied.