Results 1 - 10 of 29541
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[en] This paper addresses a wideband reflector constructed using just a single-layer subwavelength grating with multi-subpart profiles. The properties of the grating reflector are investigated by rigorous coupled-wave analysis. It is shown that for a transverse electric (TE) polarized wave, over a broadband spectrum of 1.47–2.1 μm, the reflector demonstrates high reflectivity (R0 > 98.5%) and a wide angular bandwidth (about 28°) at 1.8 μm. The effects of deviation from the design parameters on the reflection spectra are also presented. (paper)
[en] This paper describes a new method for the simultaneous measurement of the integrated reflectivity of a crystal for multiple orders of reflection at a predefined Bragg angle. The technique is demonstrated with a mica crystal for Bragg angles of 43o, 47o, and 50o. The measured integrated reflectivity for Bragg reflections up to the 24th order is compared with new theoretical predictions, which are also presented in this paper
[en] An analytical expression for reflection of neutrons from potentials with smooth boundaries, when smoothness is described by the Eckart function, is obtained and used for fitting experimental data. The analytical fitting is shown to be 7 times faster than the numerical one, based on Parrat matrix approach
[en] Measurements of the optical reflection spectra from periodic structures with two quantum wells in the elementary cell have been done. The dependencies of the light reflection on the angle of the light incidence, polarization and temperature were studied. An analysis of the experimental data showed that the pattern with 60 cells is a good Bragg reflector with reflectivity more than 90% in the maximum of the spectral band. (paper)
[en] A high-resolution study of X-ray scattering from a laterally structured surface is reported. Total external reflection displays a distinct dip in the reflectivity for incident angles θ<θc (critical angle) and around a Bragg peak a system of truncation rods is found. Generalized Fresnel equations in conjunction with a kinematical theory provide a quantitative explanation of both findings. The method is well suited for characterising modulations on a mesoscopic length scale. (orig.)
[en] A method for determining the reflection coefficients of optical elements, which is based on the use of a reflection interferometer, is proposed. The results of measurements with a He–Ne laser for several samples with different reflectivity levels are presented. Comparison with results of conventional measurements is made. The gain from the use of the reflection interferometer is estimated.
[en] A development of the theory of multilayer systems is presented. It shows precisely how to calculate thicknesses and number of layers to get reflectivity close to unity for a given arbitrary critical angle. Application of the proposed approach to real systems is demonstrated
[en] We show that in reflection from a periodic density-modulated homogeneously broadened resonant medium, the maximum of the reflectivity spectral distribution can be substantially shifted from the resonant frequency. This shift takes opposite signs depending on whether the wavevector of the density distribution is smaller or larger than the Bragg condition value
[en] A dual-resonant reflector is proposed to suppress the radio frequency breakdown and enhance the reflection in a high power relativistic backward wave oscillator. The backward wave is reflected by two reflector cavities step by step, therefore, a high reflectivity is obtained. A preliminary high power microwave generation experiment of backward wave oscillator (BWO) with a general resonant reflector and a dual-resonant reflector was carried out. A microwave with power over 3 GW, frequency 9.6 GHz, efficiency 30%, and pulse width 22 ns was generated. The experiment results show that the efficiency of BWO with a dual-RR is enhanced about 2%-6%.
[en] For weak fields, I obtain the reflectivity from a spatially-modulated resonant medium. For small modulation wavevectors, the frequency shift and the reflectivity spectral-width are reduced. For larger modulation wavevectors, a steep fall of the spectral-shape on the ultraviolet side develops, which may create a spectral hole in the vicinity of the resonance