Photonic crystals are periodic dielectric structures having periodicity of the order of the wavelength. Consequently, they o er the ability to control the propagation of electromagnetic waves in a similar way as the periodic potential a ects the electron motion in a semiconductor crystal. By choosing the parameters of the photonic crystal, desired dispersion characteristics such as band gaps for light can be implemented, providing the possibility of creating miniaturized photonic components for integrated optical circuits. In this thesis, two-dimensional photonic crystal components with passive and active functionalities are designed, realized and investigated. The passive components, including photonic crystal cavities, waveguides and tight waveguide bends, are studied by means of fareld and neareld (heterodyne SNOM) measurement techniques addressing loss, quality factors and transmission e ciencies. The ability to tune or modulate the optical properties of photonic crystal devices increases their functionality and opens up new possibilities for applications. We present two ways of perturbing the optical environment near a photonic crystal cavity, enabling tuning and modulation of the in-plane transmission. Optical switching and wavelength tuning is obtained by means of induced thermal and plasma dispersion e ects when focusing a laser onto a photonic crystal cavity structure, demonstrating the feasibility of high-speed optical integrated circuits based on silicon structures. On the other hand, tuning of the resonant wavelength and on-o switching of the transmission signal is achieved by probing the optical eld con ned within the resonant cavity by means of an atomic force microscope (AFM) tip, suggesting an integrated on-o switch or tunable lter. This thesis combines design, fabrication and measurement, thus bringing a better understanding of the fundamental properties of these types of photonic crystals, and helping to pave the way to practical integrated optical circuits.

We present all-optical tuning and switching of a microcavity inside a two-dimensional photonic crystal waveguide. The photonic crystal structure is fabricated in silicon-on-insulator using complementary metal-oxide semiconductor processing techniques based on deep ultraviolet lithography and is completely buried in a silicon dioxide cladding that provides protection from the environment. By focusing a laser onto the microcavity region, both a thermal and a plasma dispersion effect are generated, allowing tuning and fast modulation of the in-plane transmission. By means of the temporal characteristics of the in-plane transmission, we experimentally identify a slower thermal and a fast plasma dispersion effect with modulation bandwidths of the order of several 100 kHz and up to the gigahertz level, respectively.

We present theoretical and experimental results on switching and tuning of a two-dimensional photonic crystal resonant microcavity by means of a silicon AFM tip, probing the highly localized optical field in the vicinity of the cavity. On-off switching and modulation of the transmission signal in the kHz range is achieved by bringing an AFM tip onto the center of the microcavity, inducing a damping effect on the transmission resonance. Tuning of the resonant wavelength in the order of several nanometers becomes possible by inserting the AFM tip into one of the holes of the Bragg mirror forming the microcavity in the propagation direction.

We apply heterodyne scanning near-field optical microscopy (SNOM) to observe with subwavelength resolution the amplitude and phase of optical fields propagating in several microfabricated waveguide devices operating around the 1.55 mu m wavelength. Good agreement between the SNOM measurements and predicted optical mode propagation characteristics in standard ridge waveguides demonstrates the validity of the method. In situ observation of the subwavelength-scale distribution and propagation of optical fields in straight and 90 degrees bend photonic crystal waveguides facilitates a more detailed understanding of the optical performance characteristics of these devices and illustrates the usefulness of the technique for investigating nanostructured photonic devices. (c) 2005 Optical Society of America.

In this work, we investigate the transmission properties of tunable resonant cavities inside photonic crystal waveguides. We present an optical and a mechanical way of perturbing the optical environment near the resonant cavity enabling tuning and modulation of the in-plane transmission. We have discussed different ways that change the transmission properties of cavities in photonic crystals. Optical switching and wavelength tuning is obtainable by means of induced thermo and electro optical effects. These results indicate the feasibility of high-speed optical integrated circuits based on silicon photonic crystal structures. In addition, simulations have shown that an AFM tip can be used for tuning and damping. These results suggest a stand-alone MEMS solution to create a chip-based on-off switch or tunable filter. Furthermore, one could attempt to integrate more than one silicon tip to combine filter and tuning functionalities on one device. By separately controlling the position of the different tips a programmable integrated optical circuit with higher integration density and functionality could be achieved

We apply heterodyne scanning near-field optical microscopy (SNOM) to observe with subwavelength resolution the amplitude and phase of optical fields propagating in several microfabricated waveguide devices operating around the 1.55 microm wavelength. Good agreement between the SNOM measurements and predicted optical mode propagation characteristics in standard ridge waveguides demonstrates the validity of the method. In situ observation of the subwavelength-scale distribution and propagation of optical fields in straight and 90 degrees bend photonic crystal waveguides facilitates a more detailed understanding of the optical performance characteristics of these devices and illustrates the usefulness of the technique for investigating nanostructured photonic devices.

We present results of the optical characterization of silicon photonic crystal waveguides and microcavities that are completely buried in a silicon dioxide cladding and are fabricated by deep ultraviolet (UV) lithography. The advantages of buried waveguides and deep UV lithography are discussed. Transmission spectra and loss factors for photonic crystal waveguides, as well as quality factors for resonant microcavities, are obtained. The observed characteristics are in good agreement with three-dimensional simulations.

A practical and detailed analysis of light propagation around a 90 /spl deg/C bend corner in a photonic crystal slab is presented. Transmision spectra of samples with different designs are compared for better understanding of the transmission efficiency and the losses. Points where the reflection occurs can be identified by Fourier transformation of the transmission spectrum. The fringe contrast of the Fabry-Perot modulation may also allow the evaluation of the losses in the waveguide by calculating the loss coefficient.

We report the fabrication of widely tuneable (627–702nm) optically pumped two-dimensional distributed feedback polymer lasers that utilize a red-emission fluorene copolymer as the active gain medium. The lasers exhibit efficient, low threshold operation and emit highly directional output beams as a result of the enhanced two-dimensional photonic confinement provided by the employed resonator. Their emission and operating characteristics are described in detail. We demonstrate that the very wide spectral range (Δλ⩾75nm) over which these lasers can be systematically tuned is in very good agreement with theoretical predictions based on a simple waveguide model. In addition, we show that the lasers have long operating lifetimes τ1∕2⩾2×107 pulses and we discuss the impact that degradation has on the laser output characteristics.

Recent results of our studies into optical effects where sub-micron length scales play a pivotal role are presented. We start with a discussion of fine optical features produced by relatively large objects, and then move on to consider the big effects that can be produced by sub-micron structures. Topics covered include fine structure in the optical field of microlenses and gratings, and then further down in length scale from microstructured surfaces to resonant filters, photonic crystal waveguides and metallic nanoparticles. For each step we demonstrate potential applications in which such a length scale can present important advantages, as well as discussing some of the disadvantages and challenges in the design and fabrication of such elements. We particularly highlight the sensitivity of many of the structures to small variations in optical situation (e.g. geometry, orientation, material, polarization) leading significant optical effects for small-scale changes. Methods for the characterization of optical fields produced by objects at these smaller dimensions are also presented.

We will present experimental and theoretical studies of optical fields with subwavelength structures, in particular phase singularities and coherent detection methods with nanometric resolution. An electromagnetic field is characterized by an amplitude, a phase and a polarization state. Therefore, experimental studies require coherent detection methods, which allow one to measure the amplitude and phase of the optical field with subwavelength resolution. We will present two instruments, a heterodyne scanning probe microscope (heterodyne SNOM) and a high resolution interference microscope (HRIM). We will review some earlier work using the heterodyne SNOM, in particular the measurement of phase singularities produced by a 1 μm pitch grating with 10 nm spatial sampling. Using the HRIM we have investigated the intensity and phase distributions (with singularities) in the focal region of microlenses. The measurements are compared with the results calculated by rigorous diffraction theory.

We present two methods based on the analysis of Fabry-Pérot interference for a detailed characterization of a 90° corner in a two-dimensional photonic crystal waveguide fabricated in a thin Si membrane. These methods are a means of identifying the critical waveguide elements in the process of improving photonic crystal devices. The effects of the elements forming the photonic crystal waveguide are identified and quantified by means of a stage-by-stage analysis. By Fourier transforming the transmission spectra we observe the amount of light that is back reflected inside the waveguide and based on the fringe contrast of the Fabry-Pérot modulation we calculate the loss contribution of each waveguide element, such as the tapers and the 90° corner.

We present recent applications of one-dimensional (1D) and two-dimensional (2D) periodic structures. The structures were designed using rigorous diffraction theory and produced by modem micromachining techniques (electron beam writing, optical lithography). In addition, interferometric recording of periodic structures was investigated in order to fabricate periodic structures with arbitrary profile shapes.

We present dynamically reconfigurable photonic crystal nanobeam cavities, operating at ~1550 nm, that can be continuously and reversibly tuned over a 9.5 nm wavelength range. The devices are formed by two coupled nanobeam cavities, and the tuning is achieved by varying the lateral gap between the nanobeams. An electrostatic force, obtained by applying bias voltages directly to the nanobeams, is used to control the spacing between the nanobeams, which in turn results in tuning of the cavity resonance. The observed tuning trends were confirmed through simulations that modeled the electrostatic actuation as well as the optical resonances in our reconfigurable geometries. High quality factor photonic crystal nanobeam cavities, " Appl. " Quantum nature of a strongly coupled single quantum dot-cavity system, Digital resonance tuning of high-Q/Vm silicon photonic crystal nanocavities by atomic layer deposition, " Appl. tuning of photonic crystal cavities using chalcogenide glasses, " Appl. Aligning microcavity resonances in silicon photonic-crystal slabs using laser-pumped thermal tuning, " Appl. Optically tunable microcavity in a planar photonic crystal silicon waveguide buried in oxide, " Opt. Emission spectrum of electromagnetic energy stored in a dynamically perturbed optical microcavity, " Opt. Scanning a photonic crystal slab nanocavity by condensation of xenon, " Appl.crystal electric tuning of a photonic crystal laser, " Appl. Design of a silicon nitride photonic crystal nanocavity with a Quality factor of one million for coupling to a diamond nanocrystal, " Opt. Rue, " Ultra high quality factor one dimensional photonic crystal/photonic wire micro-cavities in silicon-on-insulator (SOI), " Opt. A picogram-and nanometre-scale photonic-crystal optomechanical cavity, Coupling-induced resonance frequency shifts in coupled dielectric multi-cavity filters, " Opt. Tunable coupling regimes of silicon microdisk resonators using MEMS actuators, " Opt. Resonant scattering and second-harmonic spectroscopy of planar photonic crystal microcavities, " Appl. Polarization control and sensing with two-dimensional coupled photonic crystal microcavity arrays, " Opt. Light scattering and fano resonances in high-q photonic crystal nanocavities, " Appl.