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We have simulated the coupling loss of three types of Inverse Taper and taper-lensed fiber using three dimensional (3D) semi-vectorial beam propagation methods (BPM) respectively. Our results showed that the performances of exponential inverse taper and quadratic inverse taper were better than the commonly used linear inverse taper. Especially, for TM mode the improvement in the reduction of devices size is 53% and 136% for exponential and quadratic inverse taper compared with the linear inverse taper. 相似文献
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The spectral response of an arrayed-waveguide grating (AWG) demultiplexer is calculated by simulating the field propagation in the output section of an AWG with a wide-angle beam propagation method (BPM) in a cylindrical coordinate system. As in a practical design of an AWG demultiplexer, each output waveguide consists of two straight sections connected by a bending section. The spectral response obtained by the present algorithm is more accurate than those obtained with two popular approximate methods, namely, the conventional overlapped integral method and the standard BPM for radially straight and infinitely long output waveguides. With the present algorithm, the dependence of the spectral response on the parameters of the output section is analyzed. The channel crosstalk and the 3 dB passband width of the spectral response depend mainly on the length of the first straight section, the end separation and the angular separation of the output waveguides. The bending section results in an asymmetrical spectral response with remarkable sidelobes which can be reduced by increasing the bending radius. 相似文献
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进一步研究二个问题:(1)理论模拟的方法由快速傅里叶束传播法(FFT-BPM)改为有限差分束传播法(FD-BPM),并比较了两者的优缺点。(2)模拟设计了对象提高为由GeSi合金单模脊形光波导组成的Y级联1×4光分束器。结果表明,有限差分束传播法比快速傅里叶束传播法及显形有限差分束传播法(EFD-BPM),除了数学比较容易外,计算速度也快一些。尤其是对传播步长Δz的敏感性,有限差分束传播法远没有快速傅里叶束传播法那样严重,便利了束传播法方法的采用。正如束传播法成功地应用于GeSi合金光波导及Y分支器的理论设计,现在用了1×4Y级联分束器同样得到预想的结果。光束在分束器中传播逐步分成二束再分为四束。符合设计要求。 相似文献
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High‐quality single‐crystal and polycrystalline chemical‐vapor‐deposition diamond detectors with platinum contacts have been tested at the white‐beam X28C beamline at the National Synchrotron Light Source under high‐flux conditions. The voltage dependence of these devices has been measured under both DC and pulsed‐bias conditions, establishing the presence or absence of photoconductive gain in each device. Linear response consistent with the theoretically determined ionization energy has been achieved over eleven orders of magnitude when combined with previous low‐flux studies. Temporal measurements with single‐crystal diamond detectors have resolved the nanosecond‐scale pulse structures of both the NSLS and the APS. Prototype single‐crystal quadrant detectors have provided the ability to simultaneously resolve the X‐ray beam position and obtain a quantitative measurement of the flux. 相似文献
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Rahim Ghayour Mohammad Taghi Fathi Ahmad Naseri Taheri 《Optics & Laser Technology》2008,40(5):697-702
In this paper a simple low-loss planar waveguide wide-angle bend is proposed and analyzed. The waveguide bend of this work consists of a curved tapered angle such that its tapering can be adjusted for a minimum loss (maximum transmission coefficient) and small dimension of bend. The analysis is done using wide-angle BPM (beam propagation method) type Pade (4,4). The simulated results of different bends show that at the same transmission coefficient the area required for the proposed bends are smaller than those of the abrupt bends. 相似文献
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Willem Jespers Grgory Verdon Jhonny Azuaje Maria Majellaro Henrik Kernen Xerardo García‐Mera Miles Congreve Francesca Deflorian Chris de Graaf Andrei Zhukov Andrew S. Dor Jonathan S. Mason Johan qvist Robert M. Cooke Eddy Sotelo Hugo Gutirrez‐de‐Tern 《Angewandte Chemie (International ed. in English)》2020,59(38):16536-16543
We present a robust protocol based on iterations of free energy perturbation (FEP) calculations, chemical synthesis, biophysical mapping and X‐ray crystallography to reveal the binding mode of an antagonist series to the A2A adenosine receptor (AR). Eight A2AAR binding site mutations from biophysical mapping experiments were initially analyzed with sidechain FEP simulations, performed on alternate binding modes. The results distinctively supported one binding mode, which was subsequently used to design new chromone derivatives. Their affinities for the A2AAR were experimentally determined and investigated through a cycle of ligand‐FEP calculations, validating the binding orientation of the different chemical substituents proposed. Subsequent X‐ray crystallography of the A2AAR with a low and a high affinity chromone derivative confirmed the predicted binding orientation. The new molecules and structures here reported were driven by free energy calculations, and provide new insights on antagonist binding to the A2AAR, an emerging target in immuno‐oncology. 相似文献
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较详细地介绍了合肥光源逐圈束流位置测量(turn-by-turn)系统设计思想和理论分析。该系统是为了判定二期工程升级后的注入系统的注入效率和Damping率,研究Beta振荡和轨迹瞬时变化以及其他束流动力学问题如工作点变化等的研究而研制。选择了新近受到广泛重视的对数比电路服务束流瞬时位置信号的处理。利用工作在204MHz的对数比电路完成被激励束的turn-by-turn位置测量和相空间检测。给出了该系统各部分性能和理论分析结果,介绍了快速多通道ADC在该系统的数据获取中的应用。 相似文献