Filling the liquid crystals (LCs) into the air holes of the photonic crystal fibers (PCFs), we can obtain the liquid-crystal photonic crystal fibers (LCPCFs). Due to the tunable optical properties of the LCs, we can fabricate tunable optical devices based on the LCPCFs. In this thesis, we investigate the photonic bandgap (PBG) properties and find out the effective modal index curves of the LCPCFs by the finite-difference frequency-domain (FDFD) method. The effects of the operation temperature and the alignment of the LCs are discussed. When the alignment of the LC is in the transverse plane of the PCF, we can observe the blue shift and the splitting of the PBGs as we increase the operation temperature. As the LC is aligned along the PCF, the red shift occurs and the splitting disappears. The shift and the splitting of the PBGs are due to the high anisotropic property of the LCs. Besides, we can rotate the alignment of the LCs by the external electric field, and the effects of the alignment on the propagation properties of the LCPCFs are larger than those of the operation temperature. In the experiment, we successfully fabricate the LCPCFs by using the vacuum method. In the measurement of the LCPCF at different operation temperatures,the red shift of the spectra can be observed with the increasing operation temperatures, which has a very good agreement with the simulation results. As we vary the alignment of the LCs with the external electric field, the transmission bands are almost the same as the voltage is less than 200V. During the range of 200V to 400V, the PBGs demonstrate obvious variations and the deep appears at 1050nm. When the external electric field is raised to 400V, the shapes of the spectra are almost the same and the red shift of the PBGs can be observed. The results of our simulation and the experiment measurement can help us to design and fabricate optical devices based on the LCPCFs.

Integrated photonic circuits require small photonic elements. Recent progress in nanowire synthesis and nanofabrication enables us to investigate the potential of nanowires in novel integrated photonic devices. This thesis explores light manipulation on two material platforms – metallic nanostructures that support surface plasmon polaritons (SPPs), and periodic dielectric arrays for mode engineering. In Chapters 2 and 3, I will show that chemically-synthesized metallic nanowires are attractive candidates to support SPPs and enhance light- matter interactions. The first model device consists of a single quantum emitter in close proximity to a highly crystalline Ag nanowire. When the quantum emitter is optically excited, its emission rate is enhanced by a factor of 2.5, and 60% of the emission couples into the Ag nanowire, generating single SPPs. In addition to optically exciting SPPs, we demonstrate an optoelectronic device that generates and detects SPPs electrically, paving the way for seamless integration between electronic and plasmonic elements in a single circuit. In Chapter 4, I present a general strategy to create stretchable and flexible photonic devices. Flexible photonics has garnered a lot of interest because mechanical properties can be exploited to generate highly conformal devices with novel optical characteristics. We fabricated Si nanowire photonic crystal cavities and transferred them into polydimethylsiloxane (PDMS). The composite photonic crystal cavity supports high quality factor (Q) modes in the telecommunication range. We achieve mechanical reconfiguration of the cavity by stretching it, and observe tuning of the resonance wavelength over 67 nm, 134 times the resonance linewidth. The above demonstrations, when taken together, underscore the promise and potential of nanowires in integrated photonic circuits. / Chemistry and Chemical Biology

Photonic crystal (PtC) cavities are an increasingly important way to create all optical methods to control optical data. Not only must the data be controlled, but interfacing it with high frequency electrical signals is particularly interesting especially if this occurs in the 1.55µm telecom band. We present an experiment that uses Rayleigh surface acoustic waves (SAWs) to modulate the frequency of the guided mode of an L3-cavity PtC created on a silicon slab. This work has the potential to interface optical and electrical signals via a mechanical strain wave operating at gigahertz frequencies. Defects are carefully designed into a triangular lattice PtC to realize a waveguide coupled optical cavity. The cavity can be experimentally accessed through grating couplers excited by polarized light at 10 degrees incidence from normal. The optical components are fabricated on a silicon-on-insulator platform, with light confined to the silicon slab region. Through transmission experiments, the L3 cavity was found to have a narrow resonance characterized by a Lorentzian distribution. A quality factor of 165 centered at 6255 1/cm (1.599µm) was measured. Aluminum interdigitated transducers (IDTs) were fabricated through a lithography liftoff process. Their ability to create SAWs requires a piezoelectric medium. As silicon does not have this property, growth of a thin ZnO film was required. The transducers were measured using a network analyzer and were found to produce Rayleigh SAWs at a frequency of 179MHz and a wavelength of 24µm. The acoustic energy traveled 70µm to the target optical device. The L3 cavity has dimensions of around 4µm a side - less than 1/2 a SAW wavelength. Modulation of the L3 PtC resonant frequency was monitored through a repeat of the transmission experiment but with RF excitation of the IDTs at the SAW frequency. A broadening of the transmission spectrum was expected. Unfortunately no change in the fitting parameters could be measured. An HF etch was used to undercut the L3 PtC such that a silicon slab suspended in air could be realized. Simulations had been conducted showing an order of magnitude increase in the quality factor was possible. Broken wirebonds on the transducers created unintended etch channels rendering the SAW non-operational. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2013-04-29 12:33:49.254

Dans le monde moderne de l'information numérique, les volumes de transfert de données augmentent constamment et créent une demande correspondante pour des vitesses de transfert plus élevées et un traitement des données plus rapide.De nos jours, le transfert d'information sur la puce au moyen de signaux électriques commence à atteindre ses limites en raison des restrictions physiques des effets quantiques, rendant le transfert de données au moyen de signaux optiques attrayant pour le transfert d'information rapide sur les puces informatiques. Il en résulte que la photonique au silicium, qui utilise du silicium (à motifs) en tant que milieu optique (par exemple des cristaux photoniques), a un grand potentiel pour remplacer les parties des interconnexions métalliques actuelles par celles optiques.Il existe déjà une gamme de composants photoniques créés de manière monolithique sur des plaquettes de silicium sur isolant, mais il manque encore des sources compactes de lumière pulsée sur puce. Dans cette thèse, nous travaillons sur la création de telles sources de lumière pulsée, tout en étudiant l'interaction des lasers à cristaux photoniques avec l'absorbant saturable de graphène. Bien que n'atteignant pas réellement le but ambitieux et à long terme associé à la réalisation d'un laser à verrouillage de mode intégré, cette thèse a fait quelques progrès dans cette direction. Nous avons franchi quelques étapes, telles que l'intégration du graphène et des structures actives des cristaux photoniques, l'étude de l'interaction du graphène avec les lasers compacts, le développement d'un modèle théorique permettant d'étudier cette interaction et enfin la conception de multimodes et de cavités compactes à base de cristaux photoniques pour la miniaturisation de lasers à verrouillage de mode. Ces étapes seront importantes pour le développement de dispositifs compacts capables de générer un train d'impulsions optiques sub-picosecondes dans des plates-formes à puce. / In the modern world of digital information, data transfer volumes are constantly increasing and create a corresponding demand for higher transfer speeds and faster data processing.Nowadays, the information transfer on-chip by means of electrical signals begin to reach its limitations due to physical restrictions of quantum effects, making data transfer by the means of optical signals to become an attractive prospect for high-speed information transfer on computer chips. As a result, silicon photonics, which uses (patterned) silicon as an optical medium (e.g. photonic crystals), has a great potential to replace parts of the current metallic interconnects by the optical ones.There is already a range of photonic components created monolithically on silicon-on-insulator wafers, however, compact sources of pulsed light are still missing on-chip. In this thesis, we are working on creation of such sources of pulsed light, while investigating the interaction of photonic crystal compact lasers with graphene saturable absorber. Although not actually achieving the long-term and ambitious goal associated with the realization of an integrated mode-locked laser, this thesis made some progress in that direction. We have achieved a few milestones, such as the integration of graphene and active photonic crystal structures, the study of the interaction of graphene with compact lasers, the development of a theoretical model providing a basis for studying this interaction and finally the design of multimode and compact photonic crystal based cavities for the miniaturization of mode-locked lasers. These steps will be of importance for the development of compact devices capable of generating a train of sub-picosecond optical pulses in chip-based platforms.

No description available.

For the last 20 years, there has been considerable interest in chiral nematic liquid crystal band edge lasers. The birefringent molecules of chiral nematic liquid crystals form a periodic helical structure, which results in a photonic bandgap for circularly polarised light with the same sense of rotation as the helix. A large increase in effective gain is seen for a fluorescent gain medium within the liquid crystal at the band edges, resulting in lasing. Applications of liquid crystal lasers could include miniature medical diagnostic tools, large-area holographic laser displays, and environmental sensing. The wavelength of emission from dye-doped chiral nematic liquid crystals is highly flexible, with lasers demonstrated across the visible range and near infra-red. This thesis investigates two routes for improving the functionality of chiral nematic liquid crystal lasers, supported by mathematical modelling of expected lasing wavelengths based on reflection and transmission by anisotropic layers. Perovskite is tested as a replacement for fluorescent laser dyes as a gain medium,both in the form of quantum dots dispersed in liquid crystal, and as films placed in liquid crystal structures. It is shown that while the perovskite tested provides some emission, it is not compatible for lasing in these devices, and suggestions for building on these results are made. In-plane switching is tested and developed as a means to achieve tuning of the laser wavelength, demonstrating a continuous wavelength shift of 15 nm, from 600.71 nm to 585.03 nm, over a voltage range of 100 V. This is an improvement on previous tuning in related devices, and may be extended with optimisation of cell thickness,electrode geometry, and initial lasing wavelength. Accurate descriptions of the refractive index profile of the liquid crystal and perovskite are developed and included in mathematical modelling, in addition to descriptions of the wavelength-dependent gain of a laser dye and perovskite. Suggestions for developing this modelling are made, particularly by the inclusion of accurate modelling of the distortion caused by in-plane switching.

Doctor of Philosophy (PhD) / Photonic crystals are optical structures that contain a periodic modulation of their refractive index, allowing them to control light in recent years of an unprecedented capacity. Photonic crystals may take on a variety of configurations, in particular the photonic crystal cavity, which may “hold” light in small volumes comparable to the light’s wavelength. This capability to spatially confine light opens up countless possibilities to explore for research in telecommunications, quantum electrodynamics experiments and high-resolution sensor applications. However, the vast functionality potentially made available by photonic crystal cavities is limited due to the difficulty in redefining photonic crystal components once they are formed in their (typically) solid material. The work presented in this thesis investigates several approaches to overcome this issue by reconfiguring photonic crystal cavities.

Thesis (Ph. D.)--University of Texas at Dallas, 2006. / Includes vita. Includes bibliographical references (leaves 138-149).

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Dennis W. Prather, Dept. of Electrical and Computer Engineering. Includes bibliographical references.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Dennis Prather, Dept. of Electrical and Computer Engineering. Includes bibliographical references.