186 research outputs found
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
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
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
Stretched-coordinate PML in 2D TLM simulations
A novel implementation of the stretched coordinate perfectly matched layer (PML) is presented for the two-dimensional (2D) transmission line modelling (TLM) method. The formulation offers a unified approach and is based on the mapping of the TLM node to a complex stretched domain for which the resulting transformation of the constituent RLC transmission line components is elaborated. The transformation is shown to modify the TLM connect-scatter algorithm. The absorption performance is demonstrated by simulating a canonical waveguide test case. Unlike the existing split-field based TLM-PML implementations, which are better suited to lossless media, the numerical results obtained show the proposed PML formulation is effective in the termination of both lossy and lossless media
Installed antenna performance in airborne radomes of different profiles
In this paper, broadband interactions between an antenna and a radome are modelled using a full wave numerical solver. By accurately describing both the antenna and the radome geometry with a single numerical method, a comprehensive prediction of the performance of the coupled antenna and radome installation is provided. The paper compares how different airborne dielectric radome profiles affect the antenna performance, predicting effects not seen in uncoupled simulations
Modelling of dispersive PT-symmetric Bragg grating
This paper reports on the time-domain numerical model of a parity-time Bragg grating with saturated and dispersive gain. The model is compared against the ideal PT scenario where the gain is constant and unsaturated for all frequencies
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