光学滤波片薄膜镀制工艺中的监控技术模拟分析

在窄带滤波器件的研制过程中，模拟分析了采用极值法对膜层厚度进行光学监控及其偏差对滤波器件光学特性的影响，并给出了一个4腔DWDM滤波片的理想工艺曲线以及模拟计算所得到光学特性的分布曲线，计算结果有利于指导高品质薄膜器件的研制，并研制出符合工业应用标准要求3腔和4腔的100GHz,200GHz的DWDM滤波片以及CWDM滤波片。     

干涉滤波法——改善高平均功率Nd：YAG激光器光束质量新思想…

提出了一种改善高平均功率Ｎｄ：ＹＡＧ激光器光束质量的新思想－－干涉滤波，并采用四镜不失调反射镜腔进行了实验研究。文中分析了四镜腔的干涉滤波在实验上观察到了干涉相消现象，研究了干涉滤波对改善光束质量的作用，与其等价的直腔相比，在相同的泵浦功率下，光束参数积下降了１／３￣１／２。实验结果表明，干涉滤波是一种行之有效的改善光束质量的方法。     

平面光子晶体环形腔滤波器的数值研究北大核心

根据光子晶体中波导与腔的耦合特性,设计了一种由波导与环形腔耦合实现窄带滤波的光子晶体结构。用有限元法分析了环形腔不同结构参数对各个端口透射光功率谱的影响,由此可以根据所需波长要求设计不同结构的环形腔滤波器结构,并可通过改变边界散射介质柱的排列和环形腔边界介质柱的半径,减少波导与环形腔之间的散射损耗,达到最佳滤波效果。文章可为密集波分复用系统中光学滤波器的集成以及窄带滤波器的设计提供一定的参考。     

六腔螺旋滤波器设计

六腔螺旋滤波器设计□吴振金（福建省南靖县无线电厂３６３６０３）六腔螺旋滤波器应用了６个螺旋谐振滤波器。它是采用螺旋谐振器来实现耦合谐振滤波器中的并联谐振回路而得名的。它用于共用天线的前端输入滤波和发射机的输出滤波。它是发射频谱控制、保证发射质量的关键...     

高功率固体激光谐振腔研究的进展

基于我们的工作和体会，对高功率固体激光腔研究的某些新进展，包括自成像和自滤波非稳腔，共轴和离轴非稳腔，折迭和离轴棱镜腔，非轴对称像散腔，可变反射率镜腔和渐变位相镜腔等作了详细评述和分析。最后，对实现高功率和高光束质量输出的物理思想和技术原理作了总结，并指出了可能的应用。     

双可调谐掺铒光纤环形腔滤波器的实验研究

提出一种基于全光纤有源环形腔结构的双可调谐窄带滤波器。它能够充分利用腔中掺铒光纤放大器(EDFA)的宽带增益特性 ,有效可调谐滤波范围达到 39nm ,并改善了腔精细度对EDFA增益非平坦度的相关性。通过改变抽运功率 ,可方便地对其精细度进行调谐 ,从而实现全光纤结构滤波器的滤波波长和精细度的双可调谐。     

有源光纤环形腔进行频率调谐窄线宽激光的方法

本文提出用有源光纤环形腔来获得精确调谐窄线宽激光的新方法，理论分析结果表明：幅值（或相位）调制产生的频宽扩展对腔带宽的影响很小，滤波输出激光的线宽约等于入射光随机初相位决定的线宽，有源腔对滤波输出激光还有光放大作用。     

带反射腔的光子晶体分插复用器

提出一种由二维光子晶体构成的四端口滤波器。该滤波器含三个微腔,其中两个是参数完全相同的波长选择性反射腔,用于波长选择性的反射反馈。另外一个是下载腔,用于下载特定的波长光波。利用耦合模式理论（CMT）分析了该滤波器的滤波特性,得出了实现完全下载滤波的条件,即通过改变两波长选择性反射腔到下载腔之间的距离,使之满足晶格周期的奇数倍。并且用FDTD方法对该器件进行了数值分析,显示了该器件上下载的的可行性。     

CPM自滤波非稳腔YAG激光器研究

把由非谐振环和凸面全反射镜构成的自滤波非稳腔应用于撞脉冲锁模Ｎｄ：ＹＡＧ激光器，改善了光束的空间质量和输出稳定性，获得发散角为２倍衍射极限，能量５０ｍＪ，脉宽１０ｐｓ的锁模脉冲，并与未加滤波小孔的ＣＰＭ非稳腔的输出性能进行实验比较。，     

单腔薄膜梳状滤波器的特性研究

用特征矩阵法研究了单腔薄膜梳状滤波器的梳状滤波特性,结果表明:当腔两边的薄膜的周期数为6时,单腔薄膜梳状滤波器就有很好的梳状滤波功能;当腔两边的薄膜的厚度增大时,梳状峰的位置向长波方向移动,梳状峰的间距增大,梳状峰的个数减少;当腔的厚度(或折射率)增大时,梳状峰的间距减小,梳状峰的个数增多,特别是当腔的厚度大到一定程度后,单腔薄膜梳状滤波器也能满足密集波分复用的要求。     

Experimental study of a generalized self-filtering unstableresonator applied to an XeCl laser

A diffraction-limited laser beam of 3.5 mJ with a pulse width of 11 ns and a brightness of 4.8×10¹³ W-cm^-2-Sr ^-1 has been obtained by applying a generalized self-filtering unstable resonator (SFUR) scheme to a short-pulse XeCl laser. In accordance with the theory, the generalized SFUR maintains the excellent properties of the SFUR, such as high transverse-mode discrimination, fast establishment of steady-state condition, and diffraction-limited output beam, but offers the possibility of having high magnification and higher mode volumes with shorter resonator lengths. It is possible to demonstrate that with the generalized SFUR, one can increase, by a factor more than two, the mode volume with respect to the confocal case by leaving the cavity length unaltered. These properties make the nonfocal SFUR particularly suitable for short-pulse excimer lasers     

A generalization of the self-filtering unstable resonator

Calculations on a generalization of the self-filtering unstable resonator (SFUR) are presented. The resonator is no longer confocal, and in principle, may have a shorter cavity length, while the other properties remain almost the same     

The penetration of EM waves through loaded apertures

In many cases, the effectiveness of an electromagnetic shield is determined by apertures that exist in the shield. To minimize the penetration of EM fields through a large aperture, the aperture is sometimes loaded with conductive material. The solution of the loaded aperture problem can be reduced to the calculation of equivalent magnetic surface currents, M&oarr;_s, that exist over the surface of the aperture. In the paper, the relevant integro-differential equations have been solved using the method of moments to determine M&oarr;_s for a small, square aperture loaded with a number of impedance sheets of practical interest. These values of M&oarr;_s have been used to calculate the magnetic and electric insertion losses of these impedance sheets. The numerical results are compared with shielding measurements that have been made on carbon composite materials and wire meshes and grids     

三维口面衍射场的复射线展开

本文利用Ｇａｂｏｒ原理把三维任意口面场表示成离散结构－波数相位空间中三维高斯函数的叠加将二维高斯基函数与相位空间谱双重正交的函数推广到三维，从而得到口有开函数。     

Design and Simulation of Pole Piece for Focusing of Multi-beam Electron Gun

The design of the aperture in the pole piece of a multi-beam confined-flow electron gun has been studied using the commercially available code OPERA 3D and validated the results using the CST particle studio, and the OmniTrak simulation tools. The results obtained by these tools are in good agreement with respect to the beam-waist radius and the throw of the electron gun. The square aperture proved to be a better option than circular aperture in providing the axisymmetric and uniform magnetic field. The shape and size of the pole piece have been optimized to enhance the laminarity of the electron beam using square aperture.     

A technique of synthesizing the excitation currents of planararrays or apertures

A technique of synthesizing or reconstructing the excitation currents of a planar array of aperture-type antennas from the known near-field patterns of the radiating source is presented. This technique uses an exact solution to the fields radiated by the aperture antenna without disregarding the source currents. Typical numerical computations have been carried out to validate the analytical technique developed. Sensitivity and stability of the numerical computations performed have been studied. The available iterative bandlimited signal extrapolation technique is used to reconstruct the aperture excitation currents only if the far-field patterns of the radiating source are known. Far-field patterns of aperture antennas measured in the laboratory were also used to reconstruct the aperture electric field distribution in the principal plane     

Statistical properties of the field diffracted by an aperture with partially coherent illumination

The statistical properties of the electromagnetic field diffracted by a plane aperture illuminated by a fluctuating field have been studied in the Fresnel zone on the basis of the theory of partial coherence. The average power distribution and the amplitude and phase of the degree of coherence have been computed for several coherence lengths of the illuminating field ranging from 1/4 to 5 times the dimension of the aperture and for two geometries of the observation points. The obtained results indicate the limits of validity of the often assumed hypothesis of spatial stationarity and of the real Gaussian approximation for the degree of coherence of the diffracted field. It turns out also that the optimum position of a receiving phase-sensitive system placed in the field diffracted by an aperture may not be the focus of the aperture, since there the concentration of average power density is accompanied by a poor coherence of the field.     

ESTAR: a synthetic aperture microwave radiometer for remote sensingapplications

ESTAR represents a new technology being developed for passive microwave remote sensing of the environment from space. The instrument employs an interferometric technique called aperture synthesis in which the coherent product from pairs of antennas is measured as a function of pair spacing. Substantial reductions in the antenna aperture needed for a given spatial resolution can be achieved with this technique. As a result, aperture synthesis could lead to practical passive microwave remote sensing instruments in space to measure parameters such as soil moisture and ocean salinity which require observations at long wavelengths and, therefore, large antennas. ESTAR is an L-band, aircraft built as part of research to develop this technique ESTAR is a hybrid real-and-synthetic aperture radiometer which employs stick antennas to achieve resolution along track and uses aperture synthesis to achieve resolution across track. Experiments to validate the instrument's ability to measure soil moisture have recently been conducted at the USDA watersheds at Walnut Gulch in Arizona and the Little Washita River in Oklahoma. The results of both experiments indicate that a valid image reconstruction and calibration have been obtained for this remote sensing technique     

Approximate pattern calculation of a leaky waveguide

A method is described for calculating the patterns of leaky waveguides radiated from the aperture in the metal wall of a waveguide with a rectangular cross section, the waveguide and the aperture being assumed of infinite length along the axis, the tangential components of the electric field on the aperture being assumed to have been prescribed. This method is accomplished by substituting a well approved elliptic cylinder for a boundary with a rectangular cross section. Measurements have been made for the leakyHguide to verify the accuracy of this method.     

Design and fabrication of a 1 m model of the 70 mm bore twinaperture superconducting quadrupole for the LHC insertions

For reasons of geometrical acceptance, 70 mm bore twin aperture quadrupoles are required in the LHC insertions. For an operating gradient of 160 T/m at 4.5 K, a design based on a four layer coil wound from two graded 8.2 mm NbTi conductors has been developed. Three 1 m single aperture quadrupoles of this design have been built and successfully tested. Thereafter, the magnets have been disassembled and the coils re-collared using self-supporting collars. In this paper, we describe the design features of the twin aperture quadrupole, and report on the initial collaring tests and procedures for collaring and final assembly of the 1 m magnet