In this thesis, we successfully fabricated patterned semiconductor substrates, edge-emitting lasers with deeply etched distributed Bragg reflectors (DBRs), two-dimensional photonic crystals (2DPCs) and two-dimensional photonic crystal microcavities (2DPC microcavities) by electron-beam lithography and inductively coupled plasma-reactive ion etching (ICP-RIE). We have obtained a minimum writing linewidth of 50nm and a maximum writing range of 500¡Ñ500µm2 in our electron-beam lithography system. Pitch arrays of 100nm pitch-diameter and 100nm separation have been formed on 100¡Ñ100µm2 semiconductor substrates. The etching depth of patterned Si substrates and patterned GaAs substrates are 50nm and 20nm, respectively. In the design of edge-emitting lasers with deeply etched DBRs, two and three pairs of DBRs were formed on the edge of laser cavity, respectively. To obtain high reflectance at wavelength (£f) = 960nm, 209nm mirror width and 240nm or 720nm air gap were fabricated. In the design of 2DPCs, a triangular array of air columns was adopted. The lattice constant (A) and column radius (R) are 742nm and 327nm, respectively. It has a band gap for TE modes corresponding to wavelength range in 936.45nm~968.85nm. We placed single defect in the 2DPCs to form 2DPC microcavities. In addition, we simulated the photonic band structure of a seven-defect 2DPC microcavity with A = 224nm and R = 56nm. We obtained a monopole defect mode at £f = 959.86nm. To measure 2DPCs and 2DPC microcavities, we have set up a micro-photoluminescence (Micro-PL) spectrum measurement system. We observed the Micro-PL intensity of the 2DPC microcavity is 4.5 times larger than 2DPCs at £f = 960nm in the same pumping power. The 2DPC microcavities show a lasing performance under optical pumping. The threshold power of 2DPC microcavities is 5.13mW~6.81mW at room temperature and decreases to 1.4mW~3.13mW at 15¢J.

The dielectric waveguide component has become a mature industry in these days in making it and understanding how it works. There are many theoretical and numerical methods to solve these waveguide modes. For example, the rigorous vectorial coupled transverse mode integral equation formulation (VCTMIE), finite-difference frequency-domain method (FDFD), vectorial beam propagation method (VBPM) and modal expansion method with simple bases (MEMSB)¡Ketc. With the exception of the MEMSB method and the alike, all these methods work very hard to handle interface boundaries and many require many terms meet the convergence requirements. In this thesis, we propose a rigorous modal expansion method based on a set of orthogonal transverse magnetic bases to analyze arbitrarily profiled 2-D cylindrical dielectric waveguides. First, we expand the mode field solution of a general multi-layered waveguide by linear combination of 1D homogeneous solutions. Magnetic and components are chosen for its continuity property across the material interface. The choice of Magnetic field over electric field also reduces the number of terms and minimizes the Gibb¡¦s phenomenon. Our new vector bases eliminate the numerical difficulty of working with the singular term of the cylindrical differential operators. When compared with the results using simple bases, we further reduce one quarter of terms without loosing any accuracy. Although the process of deriving the formulation of this vector cylindrical basis expansion technique is complex because Bessel functions and their derivatives are involved, the resulting matrix eigenvalue-eigenvector equation is much simpler than that of the simple bases and the new the result is also more accurate. We also extended the analysis to study the 2-D cylindrical dielectric waveguide problem.

Photonic crystals have the capability to control electromagnetic waves due to the existence of photonic bandgap. The devices based on photonic crystal structures usually have the advantage of substantial size reduction compared to their conventional counterparts, which may lead to miniaturization and large-scale integration of optical and optoelectronic devices.In this dissertation, several novel optical devices based on photonic crystals are designed and analyzed, including a compact power splitter, a compact polarizing beam splitter, an optical intersection of nonidentical optical waveguides, and a single mode coupled resonator optical waveguide. The simulation results show superior advantages compared to their conventional counterparts. In addition, a new fabrication method based on combining a custom-built blue laser writer and the technique of optical holography is developed for the purpose of mass production of useful photonic crystal devices.

Nonlinear optical phenomena associated with high-order soliton breakup in photonic crystal fibres and squeezed state generation in three dimensional photonic crystal microcavities are investigated. In both cases, the properties of periodically patterned, high-index contrast dielectric structures are engineered to control the dispersion and local field enhancements of the electromagnetic field. Ultra-short pulse propagation in a polarization-maintaining microstructured fibre (with 1 um core diameter and 1.1 m length) is investigated experimentally and theoretically. For an 80 MHz train of 130 fs pulses with average propagating powers in the fibre up to 13.8 mW, the output spectra consist of multiple discrete solitons that shift continuously to lower energies as they propagate in the lowest transverse mode of the fibre. The number of solitons and the amount that they shift both increase with the launched power. All of the data is quantitatively consistent with solutions of the nonlinear Schrodinger equation, but only when the Raman nonlinearity is treated without approximation, and self-steepening is included. The feasibility of using a parametric down-conversion process to generate squeezed electromagnetic states in 3D photonic crystal microcavity structures is investigated for the first time. The spectrum of the squeezed light is theoretically calculated by using an open cavity quantum mechanical formalism. The cavity communicates with two main channels, which model vertical radiation losses and coupling into a single-mode waveguide respectively. The amount of squeezing is determined by the correlation functions relating the field quadratures of light coupled into the waveguide. All of the relevant model parameters are realistically estimated using 3D finite-difference time-domain (FDTD) simulations. Squeezing up to ~20% below the shot noise level is predicted for reasonable optical excitation levels. To preserve the squeezed nature of the light generated in the microcavity, a unidirectional coupling geometry from the microcavity to a ridge waveguide in a slab photonic crystal structure is studied. The structure was successfully fabricated in a silicon membrane, and experimental measurements of the efficiency for the signal coupled out of the structure are in good agreement with the result of FDTD simulations. The coupling efficiency of the cavity mode to the output channel is ~60%.

Nonlinear optical phenomena associated with high-order soliton breakup in photonic crystal fibres and squeezed state generation in three dimensional photonic crystal microcavities are investigated. In both cases, the properties of periodically patterned, high-index contrast dielectric structures are engineered to control the dispersion and local field enhancements of the electromagnetic field. Ultra-short pulse propagation in a polarization-maintaining microstructured fibre (with 1 um core diameter and 1.1 m length) is investigated experimentally and theoretically. For an 80 MHz train of 130 fs pulses with average propagating powers in the fibre up to 13.8 mW, the output spectra consist of multiple discrete solitons that shift continuously to lower energies as they propagate in the lowest transverse mode of the fibre. The number of solitons and the amount that they shift both increase with the launched power. All of the data is quantitatively consistent with solutions of the nonlinear Schrodinger equation, but only when the Raman nonlinearity is treated without approximation, and self-steepening is included. The feasibility of using a parametric down-conversion process to generate squeezed electromagnetic states in 3D photonic crystal microcavity structures is investigated for the first time. The spectrum of the squeezed light is theoretically calculated by using an open cavity quantum mechanical formalism. The cavity communicates with two main channels, which model vertical radiation losses and coupling into a single-mode waveguide respectively. The amount of squeezing is determined by the correlation functions relating the field quadratures of light coupled into the waveguide. All of the relevant model parameters are realistically estimated using 3D finite-difference time-domain (FDTD) simulations. Squeezing up to ~20% below the shot noise level is predicted for reasonable optical excitation levels. To preserve the squeezed nature of the light generated in the microcavity, a unidirectional coupling geometry from the microcavity to a ridge waveguide in a slab photonic crystal structure is studied. The structure was successfully fabricated in a silicon membrane, and experimental measurements of the efficiency for the signal coupled out of the structure are in good agreement with the result of FDTD simulations. The coupling efficiency of the cavity mode to the output channel is ~60%. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The area of quantum information promises to deliver a range of new technologies in the fields of quantum computing and quantum communication. Devices based on semiconductor quantum dots hold great potential for the practical realisation of many of the components required in the proposed schemes. This thesis describes the development of several quantum dot devices. By integrating a quantum dot into a p-i-n diode, it was possible to control the dominant emission lines in its photoluminescence spectrum and to maximise the degree of polarisation correlation between the two photons emitted in the biexciton decay. With the same device under a magnetic field, a digital memory was demonstrated. The polarisation information of a single photon was stored as the spin of an electron inside the quantum dot, and was deterministically recovered some time later by the application of an electrical trigger. A fabrication process was developed in order to produce high quality two dimensional slab photonic crystals operating with a photonic band gap at ~ 900 nm. By placing a quantum dot into an appropriately designed H1 photonic crystal cavity, strong coupling was achieved between the dot and the monopole mode of the cavity. The vacuum Rabi splitting was found to be constant for all linear polarisations due to the unpolarised nature of the far-field of the mode. Finally, a new kind of cavity based on photonic crystal waveguides was developed. A Purcell enhancement of the in-plane spontaneous emission from a quantum dot coupled to a unidirectional photonic crystal waveguide was demonstrated.

In this work, we investigate several aspects of photonic crystal waveguides through modeling and simulation. We introduce a one-dimensional model for two-dimensional photonic crystal fibers (PCFs), analyze tapered PCFs, analyze planar photonic crystal waveguides and one-dimensional PCFs with infinite periodic cladding, and investigate transmission properties of a novel type of fiber, referred to as Fresnel fiber. A simple, fast, and efficient one-dimensional model is proposed. It is shown that the model is capable of predicting the normalized propagation constant, group-velocity dispersion, effective area, and leakage loss for PCFs of hexagonal lattice structure with a reasonable degree of accuracy when compared to published results that are based on numerical techniques. Using the proposed model, we investigate tapered PCFs by approximating the tapered section as a series of uniform sections along the axial direction. We show that the total field inside the tapered section of the PCF can be evaluated as a superposition of local normal modes that are coupled among each other. Several factors affecting the adiabaticity of tapered PCFs, such as taper length, taper shape, and number of air hole rings are investigated. Adiabaticity of tapered PCFs is also examined. A new type of fiber structure, referred to as Fresnel fiber, is introduced. This fiber can be designed to have attractive transmission properties. We present carefully designed Fresnel fiber structures that provide shifted or flattened dispersion characteristics, large negative dispersion, or large or small effective area, making them very attractive for applications in fiber-optic communication systems. To examine the true photonic crystal modes, for which the guidance mechanism is not based on total internal reflection, photonic crystal planar waveguides with infinite periodic cladding are studied. Attention will be focused on analytical solutions to the ideal one-dimensional planar photonic crystal waveguides that consist of infinite number of cladding layers based on an impedance approach. We show that these solutions allow one to distinguish clearly between light guidance due to total internal reflection and light guidance due to the photonic crystal effect. The analysis of one-dimensional PCFs with infinite periodic cladding is carried out in conjunction with an equivalent T-circuits method to model the rings that are close to the core of the fiber. Then, at sufficiently large distance from the core, the rest of the cladding rings are approximated by planar layers. This approach can successfully estimate the propagation constants and fields for true photonic crystal modes in both solid-core and hollow-core PCFs with a high accuracy. <i>Original file (released May 10, 2007) replaced Oct. 3, 2012 GMc per DePauw]</i> / Ph. D.

A single crystal sapphire optical fiber has been developed with an optical cladding that is used to reduce the number of modes that propagate in the fiber. This fiber is the first single crystal sapphire photonic crystal fiber ever produced. Fabrication of the optical cladding reduces the number of modes in the fiber by lowering the effective refractive index around the core, which limits the amount of loss. Different fiber designs were analyzed using Comsol Multiphysics to find the modal volumes of each. The MIT Photonic Bands modeling program was used to see if the first photonic band gap fiber could be achieved theoretically. The fibers were qualified using far field pattern and photodetector measurements as well as gas sensing experiments. The fibers were then exposed to a harsh environment of 1000 °C with a coating of alumina to test the resistance to scattering of the fiber. The fibers were also examined using materials characterization equipment to see how the harsh environments impacted the optical and mechanical stability of the bundled fiber. / Ph. D.

Slow photon, or light with reduced group velocity, is a unique phenomenon found in photonic crystals that theoreticians have long suggested to be invaluable for increasing the efficiency of light-driven processes. This thesis demonstrates experimentally the feasibility of using slow photons to optically amplify photochemistry of both organic and inorganic systems. The effect of photonic properties on organic photochemistry was investigated by tracing out the wavelength-dependent rate of photoisomerization of azobenzene anchored on silica opals. The application of slow photons to inorganic photochemical processes was realized by molding nanocrystalline titania into an inverse opal structure and investigating its photodegradation efficiency in relation to the photonic properties. Changes in the photodegradation efficiency were directly linked to modifications of the electronic band gap absorption as a result of the photonic properties. The highest enhancement of twofold was achieved when the energy of the slow photons overlaps with the electronic band gap absorption, such that the loss of light due to photonic stop-band reflection was significantly reduced. In addition, the strength of slow-photon amplification with respect to the macroscopic structural order was studied by introducing controlled disorder via the incorporation of guest spheres into the opal templates. For the first time, a correlation between structural order, photonic properties and a photochemical process was established. The ability to combine slow-photon optical amplification with chemical enhancement was further achieved by incorporating platinum nanoparticles in inverse titania opals where the platinum nanoparticles increased the lifetimes of the higher population of electron-hole pairs arising from slow photon. Overall, various important factors governing the slow photon enhancement were investigated in detail, including the energy of the photonic stop band, angle dependence, thickness of the film, degree of structural order, filling fraction of the dielectric material and diffusion of a second medium if present. Theoretical calculations based on scalar-wave approximation in support of the experimental findings were provided wherever possible. The findings provide a blueprint for achieving optical amplification using slow photons in the broad range of photochemical or photophysical processes.

Due to an increase of human activity, an increase health risk has emerged from the presence of pollutants in the environment. In the transition to renewable and sustainable life style, treatment of pollutants could support the shifting societies. A motivation behind material research for environmental applications is to maximize the efficiency of the materials to alleviate environmental pollution. In the case of titania, an increase of ultra-violet light absorption is needed to overcome its bandgap to produce reactive radicals, which is the basis for photocatalysis. It has been hypothesized that photonic crystal can enhance titania photocatalysis. They are structures made of at least two dielectrics with a high refractive index contrast, ordered in a periodic fashion. For a strong contrast, photonic band gaps emerge. The effect of the photonic band gap is to force complete reflection of the incoming light within its range and multiple internal reflections at its edges. By combining photonic and electronic band gap positions, it is possible to increase the absorption at the photonic band gap edges. In this thesis, fabrication method and structural analysis of titania and alumina/titania photonic structures were presented. A thorough optical analysis was performed at all steps of fabrication – beyond what previously has been reported. The photocatalytic activity was measured with two setups. Fourier Transform Infrared spectroscopy combined with arc lamps and bandpass filters was used to monitor the degradation of stearic acid in ambient air. A home-built setup was used to degrade methylene blue in solution with ultra-violet illumination. The results in this thesis show in general no correlation of the photocatalytic activity to the photonic band gap position, even though absorbance data displayed an increase absorption in this energy range. A more controlled environment might show the effect of the structure, as seen in some of the experiments.