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Stop Band (stop + band)
Selected AbstractsPhotonic Crystals from Monodisperse Lanthanide-Hydroxide-at-Silica Core/Shell Colloidal Spheres,ADVANCED MATERIALS, Issue 4 2007Y.-S. Lin A facile one-pot synthesis of size- controlled monodisperse lanthanide- hydroxide-at-SiO2 core/shell colloids is reported. The base-synthesized lanthanide-hydroxide-at-SiO2 particles are nonsticky enough to be well-suspended in solution, and they self-organize into 3D photonic crystals (see figure) that show a strong suppression of spontaneous emission in the photonic stop band. [source] Dielectric Planar Defects in Colloidal Photonic Crystal Films,ADVANCED MATERIALS, Issue 4 2004N. Tétreault A straightforward synthetic route to produce colloidal photonic crystals containing dielectric planar defects of controlled thickness (see Figure) is presented. Allowed states that arise within the stop band as a result of this doping greatly modify the reflectance properties of the crystals, in good agreement with theoretical predictions. [source] Microwave Bandgap in Multilayer Ceramic StructuresJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2006Bo Li A multilayer ceramic structure with a photonic bandgap (MC-PBG) was fabricated by a method of tape casting combined with screen printing. The MC-PBG structure is a two-dimensional array with either rectangular or hexagonal metal coils in a ceramic matrix. The metal coils are connected to the base metal layer in the ceramic substrate to form a monolithic body. The surface-wave dispersion properties of these MC-PBG structures were measured. A stop band, which is significantly influenced by the symmetrical characteristics of the inductor,capacitor (LC) arrays, was found in both the structures in the frequency range of 2.0,3.5 GHz. Because of their effective surface-wave suppression, MC-PBG structures can be used as high-performance antenna substrates to enhance the broadside gain of patch antenna devices. [source] An improved design of harmonic suppression for microstrip patch antennasMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2007M. K. Mandal Abstract Harmonic suppression is an important factor for active microstrip patch antennas radiating harmonic frequencies. Here, a novel compact low pass filter (LPF) having high filter selectivity and wide stop band is used on the microstrip feed line of the patch antenna. The 15 dB LPF stopband exist over 10 GHz while implementing area is 0.1464,g × 0.1789,g at the cutoff frequency of 3.55 GHz. The fundamental antenna operating frequency falls in the passband of the LPF. The other harmonics falls in the LPF stopband and thus attenuated. An example shows up to fourth harmonic are suppressed while total occupying area remains compact. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 103,105, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22049 [source] A self-similar fractal electromagnetic band-gap structure in the power plane with broadband suppression of ground bounce noiseMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2007Peng Zhou Abstract In this paper, a self-similar fractal electromagnetic band-gap structure with "L-Cross " slots is proposed and designed in the power plane to suppress the ground bounce noise in high-speed circuits. Both the simulation and the measured results with good agreement with each other show a low onset band stop frequency of 500 MHz and a broad stop band of about 4 GHz. When combining the structure with decoupling capacitor walls at the boundary of the power plane, a broadband GBN suppression from DC to 6 GHz can be obtained. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 190,192, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22063 [source] Two-color pump,probe experiments on silicon inverse opalsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2006C. Becker Abstract We present time-resolved pump,probe experiments in a transmission geometry using off-resonant excitation on very high-quality silicon inverse opals. We show that the nonlinear optical response can drastically be modified by tempering of the sample. The as-grown samples are dominated by an absorptive response with recovery times as short as one picosecond. For the tempered samples, both the relaxation and the scattering times increase, leading to a prominent dispersive response. The data reveal a transient blue-shift of the fundamental stop band on the order of 150 nm with transmission changes as large as a factor of five. Based on simple calculations using the Drude model we estimate corresponding refractive index changes as large as ,n = ,0.5 + i0.07. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reflectance and photoluminescence studies of InGaN/GaN multiple-quantum-well structures embedded in an asymmetric microcavityPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006D. Y. Lin Abstract Using reflectance (R) and photoluminescence (PL) measurements InGaN/GaN multiple-quantum-well (MQW) structures embedded in an asymmetric microcavity with different thickness of stacking pairs have been studied. The asymmetric microcavity structures are composed of a cavity sandwitched between the air/semiconductor interface and a mirror using distributed Bragg reflector (DBR). For the DBR with thinner AlN layers the high-reflectivity stop band locates at higher photon energy. The luminescence efficiency and the spectrum of InGaN/GaN multiple-quantum-well structures will be modified by the microcavity. A comparison of PL with R spectra shows that the emission efficiency can be enhanced by matching up the luminescence spectrum coming from the MQW and the high-reflectivity stop band. From the blue shift of the cavity modes as a function of incident angles the refractive index and cavity length can be determined. By measuring the PL spectra as a function of emission angle, it is found that the PL spectra were predominatly determined by microcavity resonances. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||