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371.
Integrated-optic double-ring resonators with a wide free spectral range (FSR) of 100 GHz are fabricated using GeO2-doped silica waveguides with a high relative refractive index difference (Δ) of 1.5%. The resonators are composed of two ring resonators comprising small ring waveguides with radii of 1.75 and 2.0 mm. The double-ring resonator module exhibited a wide FSR of 98.0 GHz, a finesse of higher than 138, a low crosstalk of less than -11.7 dB, and a low insertion loss of 6.1 dB. The measured FSR of 98.0 GHz is wider than any previously reported ring resonator composed of optical waveguides 相似文献
372.
Lightly p-doped (3×1017 cm-3) GaN grown on GaAs substrates by metal organic molecular beam epitaxy (MOMBE) shows deactivation of the residual acceptors on exposure to a microwave (2.45 GHz) hydrogen plasma at 250°C. Subsequent annealing to 350°C produces further dopant passivation, while higher temperatures (450°C) restore the initial conductivity. These results suggest that hydrogen carrier gases should be avoided during vapour phase growth of III-V nitrides 相似文献
373.
On the basis of the invariant imbedding method the disturbance theory for complex constants of propagation is proposed. This approach allows us to consider the influence of layer and anisotropic fluctuations of refractive index on the beyond-the-horizon propagation in the adiabatic approximation with the existence of an evaporation duct. Finally, the authors consider some examples of the calculations and investigate stochastic effects connected with the interaction between fluctuating and regular waveguides. 相似文献
374.
An improved impedance boundary method of moments is proposed to accurately and efficiently determine the propagation characteristics of multilayer planar optical waveguides whose refractive index profiles contain large step index changes or a graded-index region combined with step index changes. Extended impedance boundary conditions are used in the impedance boundary method of moments to replace regions in the waveguide structure which have refractive index discontinuities. Two methods for determining the extended boundary conditions include the standard transfer matrix method and a procedure utilizing a cascaded transmission line representation with successive calculation of input impedances. Simulation results show significantly improved convergence rates in the determination of propagation constants 相似文献
375.
Results from a unique analytical and experimental effort to assess low-altitude, short-range, radar detection capabilities in an evaporation ducting environment are presented. Within the horizon, the duct may shift the location of the last interference null several kilometers in range, which may cause nondetection at ranges where detection is expected and detection at ranges where detection is not expected. In addition, the evaporation duct may reduce the signal strength at ranges near the last interference peak so that detection of low-altitude, small-size, targets may not be possible until the target is much closer. At ranges near and beyond the horizon, radar signal strength depends both on the surface layer and on the mixed layer. To accurately model propagation in this region, knowledge of both surface layer and upper air meteorology Is required. An empirical model to merge the surface layer with the mixed layer has been developed. Comparisons of measured to calculated detection range indicate that the assumption of a standard atmosphere minimizes the variance of the difference between the detection ranges whereas ranges calculated using the measured surface meteorological conditions and a modified surface layer model minimizes the median of the difference 相似文献
376.
The X-ray patterns for the nematic phase in a series of side-on fixed polysiloxanes show different kinds of diffuse elements which imply complex short range ordering. A systematic structural study of the evolution of the patterns versus two molecular parameters, namely the spacer length and the length of the terminal aliphatic tails, suggests the possible occurrence of a smectic C phase for certain values of these parameters. Taking into account these tendencies, new synthesis led to a nematic-smectic C polymorphism observed for the first time in side-on fixed polysiloxanes. 相似文献
377.
S. V. Chentsov 《Russian Physics Journal》1995,38(9):936-940
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 79–83, September, 1995. 相似文献
378.
An operator sensitive to signal probability distribution is obtained, by integrating ideas from higher-order statistics and a frequency approach to signal processing. This function, based on a modified frequency domain kurtosis, assigns a level of stationarity to each signal spectrum component and enhances unsteady components over stationary sinusoids embedded in noise 相似文献
379.
Planar infinite arrays, comprising longitudinal slots cut in ridged waveguides, are analysed using a Galerkin formulation for the tangential electric field at both slot interfaces, combined with the finite element method for generating the waveguide Green function used in the integral equation. Computations agree very well with previously documented results 相似文献
380.
S. B. Vakarchuk 《Ukrainian Mathematical Journal》1996,48(4):601-606
In the spaces E q(Ω), 1 < q < ∞, introduced by Smirnov, we obtain exact order estimates of projective and spectral n-widths of the classes W r E p(Ω) and W r E p(Ω)Ф in the case where p and q are not equal. We also indicate extremal subspaces and operators for the approximative values under consideration. 相似文献