Spectral shift and Q-change of circular and square-shaped optical microcavity modes due to periodic sidewall surface roughness

Radiation loss and resonant frequency shift due to sidewall surface roughness of circular and square high-contrast microcavities are estimated and compared by using a boundary integral equations method. An effect of various harmonic components of the contour perturbation on the Whispering-Gallery (WG) modes in the circular microdisk and WG-like modes in the square microcavity is demonstrated. In both cases, contour deformations that are matched to the mode field pattern cause the most significant frequency detuning and Q-factor change. Favorably mode-matched deformations have been found, enabling one to manipulate the Q-factors of the microcavity modes.Comment: 5 pages with 6 figure

Q-factor and emission pattern control of the WG modes in notched microdisk resonators

Two-dimensional (2-D) boundary integral equation analysis of a notched circular microdisk resonator is presented. Results obtained provide accurate description of optical modes, free from the staircasing and discretization errors of other numerical techniques. Splitting of the double degenerate Whispering-Gallery (WG) modes and directional light output is demonstrated. The effect of the notch depth and width on the resonance wavelengths, Q-factors, and emission patterns is studied. Further improvement of the directionality is demonstrated in an elliptical notched microdisk. Applications of the notched resonators to the design of microdisk lasers, oscillators, and biosensors are discussed.Comment: 7 pages with 11 figures; to appear in IEEE J. Select. Topics Quantum. Electron., Jan/Feb 200

Efficient analysis and design of low-loss whispering-gallery-mode coupled resonator optical waveguide bends

Waveguides composed of electromagnetically-coupled optical microcavities (coupled resonator optical waveguides or CROWs) can be used for light guiding, slowing and storage. In this paper, we present a two-dimensional analysis of finite-size straight and curved CROW sections based on a rigorous Muller boundary integral equations method. We study mechanisms of the coupling of whispering gallery (WG) modes and guiding light around bends in CROWs composed of both identical and size-mismatched microdisk resonators. Our accurate analysis reveals differences in WG modes coupling in the vicinity of bends in CROWs composed of optically-large and wavelength-scale microcavities. We propose and discuss possible ways to design low-loss CROW bends and to reduce bend losses. These include selecting specific bend angles depending on the azimuthal order of the WG mode and tuning the radius of the microdisk positioned at the CROW bend.Comment: 8 pages with 10 figures (to appear in IEEE/OSA J. Lightwave Technology, 2007

Impact of In-Situ Radome Lightning Diverter Strips on Antenna Performance

Lightning diverter strips are commonly used to protect the antenna and sensitive equipment within an airborne radome. This paper compares the impact of solid metallic and segmented diverter strips on the radiation properties of the enclosed antenna. Solid metallic and segmented diverter strips of different segment profiles, i.e., square, circular and diamond, are considered. The paper reports how the placement of diverters on the radome and their geometric detail affect the antenna parameters, namely reflection coefficient and far field pattern. Furthermore, the surface electric field intensity on segmented diverter strips is analyzed for different shapes, sizes and separations between the metallic segments

Photonic molecules made of matched and mismatched microcavities: new functionalities of microlasers and optoelectronic components

Photonic molecules, named by analogy with chemical molecules, are clusters of closely located electromagnetically interacting microcavities or "photonic atoms". As two or several microcavities are brought close together, their optical modes interact, and a rich spectrum of photonic molecule supermodes emerges, which depends both on geometrical and material properties of individual cavities and on their mutual interactions. Here, we discuss ways of controllable manipulation of photonic molecule supermodes, which improve or add new functionalities to microcavity-based optical components. We present several optimally-tuned photonic molecule designs for lowering thresholds of semiconductor microlasers, producing directional light emission, enhancing sensitivity of microcavity-based bio(chemical)sensors, and optimizing electromagnetic energy transfer around bends of coupled-cavity waveguides. Photonic molecules composed of identical microcavities as well as of microcavities with various degrees of size or material detuning are discussed. Microwave experiments on scaled photonic molecule structures are currently under way to confirm our theoretical predictions.Comment: 10 pages with 12 figure

Coupled electrothermal two-dimensional model for lightning strike prediction and thermal modeling using the TLM method

This paper presents a fully coupled two-dimensional (2-D) multiphysics model for predicting the location of the arc discharge and lightning channel, and modeling its thermal and electrical behavior as a highly conductive plasma channel. The model makes no assumptions on the physical location of the lightning channel but predicts its appearance purely from the electromagnetic (EM) field conditions. A heat diffusion model is combined with the time-varying nature of the EM problem where material properties switch from linear air material to a dispersive and nonlinear plasma channel. This multiphysics model is checked for self-consistency, stability, accuracy, and convergence on a canonical case where an arc channel is established between two metal electrodes upon exposure to an intensive electric field. The model is then applied to the 2-D study of a diverter strip for aircraft lightning protection

Modelling chaos in asymmetric optical fibres

A ray dynamical approach is developed for the study of large-core asymmetric step index fibres (SIF), especially those made from chalcogenide glasses (ChGs) which can exhibit very high refractive index, large numerical aperture, and which are transparent at mid-infrared wavelengths. The model allows for deformations of the SIF away from concentric circular structures, and for the light rays captured by the fibre to behave chaotically within the asymmetric boundaries of the fibre. Chaotic and periodic rays can be classified by the Poincaré surface of sections (SOSs). In the model, the ray dynamics in the SIF are approximated by dividing the SOSs into pixels; the construction of a transfer matrix stores all the mapping probabilities. The light intensity distribution in the SOSs is efficiently propagated using the constructed transfer matrix, providing a viable alternative to propagating all the rays in the SIF by brute force ray tracing. The model enables the rapid calculation of the power accumulated in the fibre core following an arbitrary excitation

Photonic biosensor chip for early-stage cancer diagnosis

This paper introduces a generic design of a silicon on silica “lab on a chip” photonic biosensor for medical diagnosis applications, and especially for early-stage cancer diagnosis. The sensitivity of detection of the biosensor developed is at least 10 - 100 times more sensitive than that of current commercial biosensors