Semiconductor quantum dots and metal nanoparticles feature very strong light-matter interactions, which has led to their use in many photonic applications such as photodetectors, biosensors, components for telecommunications etc.Under illumination both structures exhibit collective electron-photon resonances, described in the frameworks of quasiparticles as exciton-polaritons for semiconductors and surface plasmon-polaritons for metals.To date these two approaches to controlling light interactions have usually been treated separately, with just a few simple attempts to consider exciton-plasmon interactions in a system consisting of both semiconductor and metal nanostructures.In this work, the exciton-polaritons and surface \\plasmon-polaritons are first considered separately, and then combined using the Finite Difference Time Domain numerical method coupled with a master equation for the exciton-polariton population dynamics.To better understand the properties of excitons and plasmons, each quasiparticle is used to investigate two open questions - the source of the Stokes shift between the absorption and luminescence peaks in quantum dots, and the source of the photocurrent increase in quantum dot infrared photodetectors coated by a thin metal film with holes. The combined numerical method is then used to study a system consisting of multiple metal nanoparticles close to a quantum dot, a system which has been predicted to exhibit quantum dot-induced transparency, but is demonstrated to just have a weak dip in the absorption. / <p>QC 20120417</p>

Surface plasmon-polaritons are optical surface waves formed through the interaction of photons with free electrons at the surface of metals. They offer interesting applications in a broad range of scientific fields such as physics, chemistry, biology, and material science. However, many of such applications face limitations imposed by the high propagation losses of these waves at visible and near-infrared wavelengths, which result mainly from power dissipation in the metal. In principle, the propagation losses of surface plasmon-polaritons can be compensated through optical amplification. The objective of this thesis is to provide deeper insights on the physics of surface plasmon-polariton amplification and spontaneous emission in surface plasmon-polariton amplifiers through theoretical and experimental vehicles applied (but not necessarily restricted) to a particular plasmonic mode termed long-range surface plasmon-polariton. On the theoretical side, the objective is approached by developing a realistic theoretical model to describe the small-signal amplification of surface plasmon-polaritons in planar structures incorporating dipolar gain media such as organic dye molecules, rare-earth ions, and quantum dots. This model takes into account the inhomogeneous gain distribution formed near the metal surface due to a non-uniform excitation of dipoles and due to a position-dependent excited-state dipole lifetime that results from near-field interactions between the excited dipoles and the metal. Also, a theoretical model to describe the amplified spontaneous emission of surface plasmon-polaritons supported by planar metallic structures is developed. This model takes into account the different energy decay channels into which an exited dipole located in the vicinity of the metal can relax. The validity of this model is confirmed through experimentation. On the experimental side, the objective is approached by providing a direct experimental demonstration of complete loss compensation in a plasmonic waveguide. The experiments are conducted using the long-range surface plasmon-polariton supported by a symmetric thin gold waveguide incorporating optically pumped organic dye molecules in solution as the gain medium. Also, an experimental study of spontaneous emission in a long-range surface plasmon-polariton amplifier is presented. It is shown that this amplifier benefits from a low spontaneous emission into the amplified mode, which leads to an optical amplifier with low noise characteristics. The experimental setup and techniques are explained in detail.

The behaviour of surface plasmon polaritons (SPPs) in nanoscale geometries is studied using numerical methods supported by theory and experiment. First, we derive the behaviour of SPPs at graded metal-dielectric interfaces, including dispersion relations, field profiles, propagation velocities, losses, and cutoff wavelength. Numerical simulations show excellent agreement with analytic solutions. In the second part of the thesis we design hybrid vanadium dioxide-plasmonic based absorption switches. The switches are designed and optimized using optical, electrical and thermal simulations. 5 $\mu$m switch designs have extinction ratios exceeding 30 dB and require powers of 10 mW. A switch is fabricated based on the proposed design. A 7 $\mu$m experimental switch reaches 16.4 dB of extinction and requires 64 mW of power, making it one of the most efficient optical switches ever demonstrated in terms of extinction and power consumption. Numerical simulations predict experimental results with a high degree of accuracy.

The behaviour of surface plasmon polaritons (SPPs) in nanoscale geometries is studied using numerical methods supported by theory and experiment. First, we derive the behaviour of SPPs at graded metal-dielectric interfaces, including dispersion relations, field profiles, propagation velocities, losses, and cutoff wavelength. Numerical simulations show excellent agreement with analytic solutions. In the second part of the thesis we design hybrid vanadium dioxide-plasmonic based absorption switches. The switches are designed and optimized using optical, electrical and thermal simulations. 5 $\mu$m switch designs have extinction ratios exceeding 30 dB and require powers of 10 mW. A switch is fabricated based on the proposed design. A 7 $\mu$m experimental switch reaches 16.4 dB of extinction and requires 64 mW of power, making it one of the most efficient optical switches ever demonstrated in terms of extinction and power consumption. Numerical simulations predict experimental results with a high degree of accuracy.

Surface plasmon-polaritons are optical surface waves formed through the interaction of photons with free electrons at the surface of metals. They offer interesting applications in a broad range of scientific fields such as physics, chemistry, biology, and material science. However, many of such applications face limitations imposed by the high propagation losses of these waves at visible and near-infrared wavelengths, which result mainly from power dissipation in the metal. In principle, the propagation losses of surface plasmon-polaritons can be compensated through optical amplification. The objective of this thesis is to provide deeper insights on the physics of surface plasmon-polariton amplification and spontaneous emission in surface plasmon-polariton amplifiers through theoretical and experimental vehicles applied (but not necessarily restricted) to a particular plasmonic mode termed long-range surface plasmon-polariton. On the theoretical side, the objective is approached by developing a realistic theoretical model to describe the small-signal amplification of surface plasmon-polaritons in planar structures incorporating dipolar gain media such as organic dye molecules, rare-earth ions, and quantum dots. This model takes into account the inhomogeneous gain distribution formed near the metal surface due to a non-uniform excitation of dipoles and due to a position-dependent excited-state dipole lifetime that results from near-field interactions between the excited dipoles and the metal. Also, a theoretical model to describe the amplified spontaneous emission of surface plasmon-polaritons supported by planar metallic structures is developed. This model takes into account the different energy decay channels into which an exited dipole located in the vicinity of the metal can relax. The validity of this model is confirmed through experimentation. On the experimental side, the objective is approached by providing a direct experimental demonstration of complete loss compensation in a plasmonic waveguide. The experiments are conducted using the long-range surface plasmon-polariton supported by a symmetric thin gold waveguide incorporating optically pumped organic dye molecules in solution as the gain medium. Also, an experimental study of spontaneous emission in a long-range surface plasmon-polariton amplifier is presented. It is shown that this amplifier benefits from a low spontaneous emission into the amplified mode, which leads to an optical amplifier with low noise characteristics. The experimental setup and techniques are explained in detail.

abstract: The study of subwavelength behavior of light and nanoscale lasing has broad potential applications in various forms of computation i.e. optical and quantum, as well as in energy engineering. Although this field has been under active research, there has been little work done on describing the behaviors of threshold and saturation. Particularly, how the gain-molecule behavior affects the lasing behavior has yet to be investigated. In this work, the interaction of surface-plasmon-polaritons (SPPs) and molecules is observed in lasing. Various phenomenologies are observed related to the appearance of the threshold and saturation regions. The lasing profile, as a visual delimiter of lasing threshold and saturation, is introduced and used to study various parametrical dependencies of lasing, including the number-density of molecules, the molecular thickness and the frequency detuning between the molecular transition frequency and the SPP resonant frequency. The molecular population distributions are studied in terminal and dynamical methods and are found to contain unexpected and theoretically challenging properties. Using an average dynamical analysis, the simulated spontaneous emission cascade can be clearly seen. Finally, theoretical derivations of simple 1D strands of dipoles are presented in both the exact and mean-field approximation, within the density matrix formalism. Some preliminary findings are presented, detailing the observed behaviors of some simple systems. / Dissertation/Thesis / Masters Thesis Chemical Engineering 2017

Over the past few years, surface plasmon photodetectors have been of renewed interest. This is due to their unique double functionality of combining an SPP waveguide structure with a photodetection structure. This thesis investigates the performance of a Schottky nano-photodetector integrated into a finite width metal stripe which is covered by air on top and supported by silicon at the bottom, supporting the propagation of bound SPP modes. Properties of surface plasmons, including the sub-wavelength confinement, were exploited to increase the efficiency of the detector. The detector performance was explored via applying end-fire coupling to the fundamental supported mode, then the results were used to calculate the devices responsivity, dark current, minimum detectable power, and photocurrent for various metal lengths. End fire coupling to a Schottky mode supported by a nano-structured metal was done for what is believed to be the first time.

Different types of plasmonic nanostructures are proposed and examined experimentally and theoretically, with a view towards sensing applications. First, a self-assembly approach was developed to create arrays of well-ordered glass-supported gold nanoparticles (AuNPs) with controllable particle size and inter-particle spacing. Then, a periodic array of gold nano-disks (AuNDs) supported by a Bragg reflector was proposed and examined in a search for Fano resonances in its optical response. Arrays of heptamer-arranged nanoholes (HNH) in a thin gold film were also proposed and explored theoretically and experimentally, revealing a very rich spectrum of resonances, several exhibiting a Fano lineshape. A commercial implementation of the vectorial finite element method (FEM) was used to model our plasmonic structures. Taking advantage of the periodic nature of the structures, a unit cell containing a single element was modelled. The transmittance, reflectance or absorbance spectra were computed, and the associated electromagnetic fields were obtained by solving the vector wave equations for the electromagnetic field vectors throughout the structures, subject to the applicable boundary conditions, and the applied source fields. The sensing performance of the structures, based on the bulk sensitivity, surface sensitivity and figure of merit (FOM) was calculated. First, a novel bottom-up fabrication approach was applied (by our collaborators) to form a periodic array of AuNPs with controllable size over large areas on SiO2 substrates. In this method, self-assembly of block copolymer micelles loaded with metal precursors was combined with a seeding growth route to create ordered AuNPs of desired size. It was shown that this new fabrication method offers a new approach to tune the AuNP size and edge-to-edge inter-particle spacing while preserving the AuNP ordering. The optical characteristics of the AuNP arrays, such as their size, interparticle spacing, localized surface plasmon resonance (LSPR) wavelength, and bulk sensitivity, were examined, numerically and experimentally. This proposed novel fabrication method is applicable for low-cost mass-production of large-area arrays of high-quality AuNPs on a substrate for sensing applications. Then, we proposed and examined the formation of Fano resonances in a plasmonic-dielectric system consisting of uncoupled gold nano-disk (AuND) arrays on a quarter-wave dielectric stack. The mechanism behind the creation of Fano resonances was explained based on the coherent interference between the reflection of the Bragg stack and the LSPPs of the AuNDs. Fano parameters were obtained by fitting the computational data to the Fano formula. The bulk sensitivities and figure of merit of the Fano resonances were calculated. This plasmonic structure supports Fano resonances with a linewidth around 9 nm which is much narrower than the individual AuND LSPP bandwidth ( 80 nm) and the Bragg stack bandwidth ( 100 nm). Supporting Fano resonances with such a narrow linewidth, the structure has a great potential to be used for sensing applications. Also, this metallic-dielectric nanostructure requires no near-field coupling between AuNDs to generate the Fano resonances. So, the AuNDs can be located far enough from each other to simplify the potential fabrication process. The optical properties of HNH arrays on an SiO2 substrate were investigated, numerically and experimentally. Helium focused ion beam (HeFIB) milling was applied (by Dr. Choloong Hahn) to fabricate well-ordered and well-defined arrays of HNHs. Transmittance spectra of the structures were obtained as the optical response, which exhibits several Fano resonances. Then, the mechanism behind the formation of the Fano resonances was explained, and the sensing performance of the structure was inspected by measuring the bulk sensitivities. This array of nanohole cluster is exciting because it supports propagating SPPs and LSPPs, and also Wood’s anomaly waves, which makes the optical response very rich in excitations and spectral features. Also, as a periodic array of sub-wavelength metallic nanoholes, the system produces extraordinary optical transmission - highly enhanced transmission through (otherwise) opaque metallic films at specific wavelengths, facilitating measurement acquisition in transmission.

In this thesis by articles, I propose and demonstrate the full design, fabrication and characterization of optical biosensors based on (Bloch) Long Range Surface Plasmon Polaritons (LRSPPs). Gold waveguides embedded in CYTOP with an etched microfluidic channel supporting LRSPPs and gold waveguides on a one-dimensional photonic crystal (1DPC) supporting Bloch LRSPPs are exploited for biosensing applications. Straight gold waveguides embedded in CYTOP supporting LRSPPs as a biosensor, are initially used to measure the kinetics constants of protein-protein interactions. The kinetics constants are extracted from binding curves using the integrated rate equation. Linear and non-linear least squares analysis are employed to obtain the kinetics constants and the results are compared. The device is also used to demonstrate enhanced assay formats (sandwich and inhibition assays) and protein concentrations as low as 10 pg/ml in solution are detected with a signal-to-noise ratio of 20 using this new optical biosensor technology. CYTOP which has a refractive index close to water is the fluoropolymer of choice in current state of the art waveguide biosensors. CYTOP has a low glass transition temperature which introduces limitations in fabrication processes. A truncated 1D photonic crystal can replace a low-index polymer cladding such as CYTOP, to support Bloch LRSPPs within the bandgap of the 1DPC over a limited ranges of wavenumber and wavelength. Motivated by quality issues with end facets, we seek to use grating couplers in a broadside coupling scheme where a laser beam emerging from an optical fiber excites Bloch LRSPPs on a Au stripe on a truncated 1D photonic crystal. Adiabatic and non-adiabatic flared stripes accommodating wide gratings size-matched to an incident Gaussian beam are designed and compared to maximise the coupling efficiency to LRSPPs. The gratings are optimized, initially, through 2D modelling using the vectorial finite element method (FEM). Different 3D grating designs were then investigated via 3D modelling using the vectorial finite difference time domain (FDTD) method. Given their compatibility with planar technologies, gratings and waveguides can be integrated into arrays of biosensors enabling multi-channel biosensing. A multi-channel platform can provide, e.g., additional measurements to improve the reliability in a disease detection problem. Thus, a novel optical biosensor based on Bloch LRSPPs on waveguide arrays integrated with electrochemical biosensors is presented. The structures were fabricated on truncated 1D photonic crystals comprised of 15 period stack of alternating layers of SiO2/Ta2O5. The optical biosensors consist of Au stripes supporting Bloch LRSPPs and integrate grating couplers as input/output means. The Au stripes also operate as a working electrode in conjunction with a neighboring Pt counter electrode to form an electrochemical sensor. The structures were fabricated using bilayer lift-off photolithography and the gratings were fabricated using overlaid e-beam lithography. The planar waveguides are integrated into arrays capable of multichannel biosensing. The wafer is covered with CYTOP as the upper cladding with etched microfluidic channels, and wafer-bonded to a borofloat silica wafer to seal the fluidic channels and enable side fluidic interfaces. The proposed device is capable in principle of simultaneous optical and electrochemical sensing and could be used to address disease detection problems using a multimodal strategy.

Surface plasmon-polaritons are optical surface waves formed through the interaction of photons with free electrons at the surface of metals. They offer interesting applications in a broad range of scientific fields such as physics, chemistry, biology, and material science. However, many of such applications face limitations imposed by the high propagation losses of these waves at visible and near-infrared wavelengths, which result mainly from power dissipation in the metal. In principle, the propagation losses of surface plasmon-polaritons can be compensated through optical amplification. The objective of this thesis is to provide deeper insights on the physics of surface plasmon-polariton amplification and spontaneous emission in surface plasmon-polariton amplifiers through theoretical and experimental vehicles applied (but not necessarily restricted) to a particular plasmonic mode termed long-range surface plasmon-polariton. On the theoretical side, the objective is approached by developing a realistic theoretical model to describe the small-signal amplification of surface plasmon-polaritons in planar structures incorporating dipolar gain media such as organic dye molecules, rare-earth ions, and quantum dots. This model takes into account the inhomogeneous gain distribution formed near the metal surface due to a non-uniform excitation of dipoles and due to a position-dependent excited-state dipole lifetime that results from near-field interactions between the excited dipoles and the metal. Also, a theoretical model to describe the amplified spontaneous emission of surface plasmon-polaritons supported by planar metallic structures is developed. This model takes into account the different energy decay channels into which an exited dipole located in the vicinity of the metal can relax. The validity of this model is confirmed through experimentation. On the experimental side, the objective is approached by providing a direct experimental demonstration of complete loss compensation in a plasmonic waveguide. The experiments are conducted using the long-range surface plasmon-polariton supported by a symmetric thin gold waveguide incorporating optically pumped organic dye molecules in solution as the gain medium. Also, an experimental study of spontaneous emission in a long-range surface plasmon-polariton amplifier is presented. It is shown that this amplifier benefits from a low spontaneous emission into the amplified mode, which leads to an optical amplifier with low noise characteristics. The experimental setup and techniques are explained in detail.