The Study of Optoelectronics in Semiconductor and Metallic Nanoparticle Hybrid Systems

This thesis examines optoelectronics of photonic crystals and photonic nanofibers, especially with quantum dots and metallic nanoparticles doped into them. The simulations produced focus on the quantum dots, which are presented in an ensemble of 3-level systems. In order to consider a photonic nanofiber in isolation, a model was developed for the density of photonic states. We studied two profiles, a square cross-section and a circular cross-section. In addition, we consider two architectures, one where a photonic crystal surrounds a dielectric fiber, and one where the fiber is another photonic crystal. We found several photonic nanofibers with a single bound photonic state and calculated the density of states. We studied dipole-dipole interactions through photon absorption in three-level quantum dots doped in a photonic nanofiber. The density matrix method was used to calculate the absorption coefficient and the mean field approximation was used to incorporate dipole-dipole interactions. It was found that a transparent state can become an absorbing state if the dipole-dipole interactions are switched on. It is also predicted that one absorbing peak can be split into two absorbing peaks through judicious selection of the resonance energies of the quantum dots and the location of the bound photon state in the nanofiber. We calculated the energy transfer and photoluminescence in donor and acceptor quantum dots which were embedded in a nonlinear photonic crystal. These quantum dots interacted via the dipole-dipole interaction. It was found that the photoluminescence of the acceptor quantum dot could be controlled by a pump laser. We have also studied the interactions between a metallic nanosphere and a quantum dot embedded on a dielectric substrate. Dipole-dipole interactions between them caused energy absorption, evaluated with the density matrix method. The absorption spectrum was found to switch from one peak to two peaks when the intensity of the control laser increased. Adding a metallic nanosphere can also cause splitting. Additionally, fluorescence efficiency in the quantum dot was found to be quenched by the presence of the metallic nanosphere. Finally, we studied quantum coherence and interference phenomena in a quantum dot and metallic nanorod hybrid system. It was predicted that the power absorption spectrum of the metallic nanorod can be switched from two transparent states to one transparent state by the control laser. These findings can be used to create ultrafast all-optical switching and sensing nanodevices. Also, the systems discussed here have applications in photovoltaics, quantum computation, and cryptography, among others

Tip-enhanced strong coupling spectroscopy, imaging, and control of a single quantum emitter

Optical cavities can enhance and control light-matter interactions. This level of control has recently been extended to the nanoscale with single emitter strong coupling even at room temperature using plasmonic nanostructures. However, emitters in static geometries, limit the ability to tune the coupling strength or to couple different emitters to the same cavity. Here, we present tip-enhanced strong coupling (TESC) with a nanocavity formed between a scanning plasmonic antenna tip and the substrate. By reversibly and dynamically addressing single quantum dots, we observe mode splitting up to 160 meV and anticrossing over a detuning range of ~100 meV, and with subnanometer precision over the deep subdiffraction-limited mode volume. Thus, TESC enables previously inaccessible control over emitter-nanocavity coupling and mode volume based on near-field microscopy. This opens pathways to induce, probe, and control single-emitter plasmon hybrid quantum states for applications from optoelectronics to quantum information science at room temperature

Probing the response of quantum plasmonic systems: from the macroscopic to the microscopic

In this thesis we investigate the response of plasmonic systems in a quantum optics setting. This work can be grouped into two sub-investigations, the study of macroscopic and microscopic responses. The narrative of the thesis comprises three principal parts. First, we give an in-depth review of the field of quantum plasmonics as it is an important theme that runs through the work contained in this thesis. In particular, we focus on outlining the cutting edge research that is being done on the intense interactions between plasmonic systems and quantum emitters. This leads naturally to the first investigation into the macroscopic response of quantum plasmonic systems in a metamaterial setting. We outline how complex hybrid systems of plasmonic metal nanoparticles (MNP) and two-level quantum dots (QD) can be used to create a quantum plasmonic metamaterial. Metamaterials are structures composed of periodic lattices of identical subwavelength unit cell scatterers, each of which governs completely the electromagnetic properties of the entire bulk material. We theorize the use of MNP-QD nanorings as a unit cell in order to control the macroscopic magnetic properties of the metamaterial. We outline how such a metamaterial can have a tunable, and saturable, magnetic permeability. In the last part of the thesis we consider the model of a single light mode interacting ultrastrongly with a collection of emitters, in the anticipation that quantum plasmonic systems can be brought into this ultrastrong-coupling regime (USC). In particular we study the emission of the system after the coupling between the light mode and the emitters is non-adiabatically switched-on. We find evidence that for both two-level, and multi-level, emitters in the USC, both the counter-rotating terms and the diamagnetic term must be included to prevent qualitative errors.Open Acces

The Optical Response of Strongly Coupled Quantum Dot- Metal Nanoparticle Hybrid Systems

In this thesis, we study, theoretically, hybrid systems composed of semiconducting quantum dots (SQDs) and metallic nanoparticles (MNPs) which are coupled by means of an applied optical field. Systems composed of SQDs and MNPs have recently been a very active area of research. Such structures are considered to be viable candidates for use in nanodevices in quantum information and nanoscale excitation transfer. The goal of this thesis is to investigate the interactions of the constituent particles and predict the hybrid response of SQD/MNP systems. We first study a single SQD coupled to a spherical MNP, and explore the relationship between the size of the constituents and the response of the system. We identify four distinct regimes of behavior in the strong field limit that each exhibit novel properties, namely, the Fano regime, exciton induced transparency, suppression and bistability. In chapter 3, we will explore these four regimes in detail and set bounds on each. In chapter 4, we then show that the response of the system can be tailored by engineering metal nanoparticle shape and the exciton resonance of SQDs to control the local-fields that couple the MNPs and SQDs. We identify regimes where dark modes and higher order multipolar modes can influence hybrid response. External fields do not directly drive MNP dark modes, so SQD/MNP coupling is dominated by the local induced coupling, providing a situation in which the induced self-interaction could be probed using near field techniques. Finally, we consider a system of two SQDs coupled to a MNP. In particular, we identify and address issues in modeling the system using a semiclassical approach, which can lead to unstable and chaotic behavior in a strong SQD-SQD coupling regime. When we model the system using a more quantum mechanical approach, this chaotic regime is absent. Finally, we compare the two models on a system with a strong plasmon-mediated interaction between the SQDs and a weak direct interaction between them

Light-Matter Interaction in Hybrid Quantum Plasmonic Systems

Attempting to implement quantum information related applications utilizing atoms and photons, as they naturally form quantum systems supporting superposition states, hybrid quantum plasmonic systems emerged in the past as a platform to study and engineer light-matter interaction. This platform combines the unrivaled electromagnetic field localization of surface plasmon polaritons, boosting the light-matter coupling rate, with the tremendous integration potential of truly nanoscale structures, and both the significant emission rates of nanoantennas and photonic transmission velocities. In this work, a classical description of surface plasmon polaritons is combined with a light-matter interaction model based on a cavity quantum electrodynamical formalism. The resulting composite semi-classical method, introduced and described in this thesis, provides efficient and versatile means to simulate the dynamical behavior of radiative atomic transitions coupled to plasmonic cavity modes in the weak incoherent coupling regime. Both the emission into the far field and various dissipation mechanisms are included by expanding the model to an open quantum system. The variety of light-matter interaction applications that can be modeled with the outlined method is indicated by the four different exemplary scenarios detailed in the application chapter of this thesis. The classical description of localized surface plasmon polaritons is benchmarked by reproducing the experimental measurements of the molecular fluorescence manipulation through optical nanoantennas in a collaborative effort with experimental partners. Furthermore, in the weak light-matter coupling regime, the potential of achieving a higher nanoantenna functionality and simultaneously realizing more elaborate quantum dynamics is revealed by the three remaining applications. Each pivotally involving a bimodal nanoantenna and demonstrating different quantum optical phenomena, the implementation of cavity radiation mode conversion, non-classical cavity emission statistics, and non-classical cavity emission properties is shown and described in the application chapter

Plasmon-assisted two-photon Rabi oscillations in a semiconductor quantum dot -- metal nanoparticle heterodimer

Tho-photon Rabi oscillations hold potential for quantum computing and quantum information processing, because during a Rabi cycle a pair of entangled photons may be created. We theoretically investigate the onset of this phenomenon in a heterodimer comprising a semiconductor quantum dot strongly coupled to a metal nanoparticle. Two-photon Rabi oscillations in this system occur due to a coherent two-photon process involving the ground-to-biexciton transition in the quantum dot. The presence of a metal nanoparticle nearby the quantum dot results in a self-action of the quantum dot via the metal nanoparticle, because the polatization state of the latter depends on the quantum state of the former. The interparticle interaction gives rise to two principal effects: (i) - enhancement of the external field amplitude and (ii) - renormalization of the quantum dot's resonance frequencies and relaxation rates of the off-diagonal density matrix elements, both depending on the populations of the quantum dot's levels. Here, we focus on the first effect, which results in interesting new features, in particular, in an increased number of Rabi cycles per pulse as compared to an isolated quantum dot and subsequent growth of the number of entangled photon pairs per pulse. We also discuss the destructive role of radiative decay of the excitonic states on two-photon Rabi oscillations for both an isolated quantum dot and a heterodimer.Comment: 11 pages, 19 figure

Optical Yagi-Uda nanoantennas

Conventional antennas, which are widely employed to transmit radio and TV signals, can be used at optical frequencies as long as they are shrunk to nanometer-size dimensions. Optical nanoantennas made of metallic or high-permittivity dielectric nanoparticles allow for enhancing and manipulating light on the scale much smaller than wavelength of light. Based on this ability, optical nanoantennas offer unique opportunities regarding key applications such as optical communications, photovoltaics, non-classical light emission, and sensing. From a multitude of suggested nanoantenna concepts the Yagi-Uda nanoantenna, an optical analogue of the well-established radio-frequency Yagi-Uda antenna, stands out by its efficient unidirectional light emission and enhancement. Following a brief introduction to the emerging field of optical nanoantennas, here we review recent theoretical and experimental activities on optical Yagi-Uda nanoantennas, including their design, fabrication, and applications. We also discuss several extensions of the conventional Yagi-Uda antenna design for broadband and tunable operation, for applications in nanophotonic circuits and photovoltaic devices