Numerical computation of the deflection fields in magnetic yokes with wedged coil-sections and in electrostatic deflectors with planar electrodes

The computational methods of deflection fields in magnetic yokes with wedged coil-sections and electrostatic deflectors with planar electrodes are discussed. The magnetic yokes with wedged coil-sections can be combined into various shapes of magnetic deflectors, which may offer a variety of choices for adjusting the deflection field distributions to reduce the deflection aberrations more effectively. An advantage of the planar electrostatic deflectors is the simplicity in structure, which might allow the deflectors to be used in the deflection array of multi-electron beam lithography systems. Based on the methods described in this paper two computer programs have been developed. As examples, the deflection field distribution of some typical deflectors have been computed.     

Analysis of electrostatic small-angle deflection

Electron beam aberrations resulting from deflection by two sets of similar, mutally perpendicular electrostatic deflectors have been studied. The analysis is applicable to the cases where the beam can be treated as a collection of noninteracting individual electrons deflected through a small angle by spatially smooth fields. The analysis shows that, with the types of electrostatic deflectors commonly used, anastigmatism cannot be achieved unless external corrections are employed.     

Broadside radiation from periodic leaky-wave antennas

A double-strip grating leaky-wave antenna consisting of two strips per unit cell is analyzed. The stopband behavior exhibited at broadside scan in the single-strip grating antenna is characteristic of all periodic leaky-wave antennas having a single strip per unit cell, and results in a drastic increase in the attenuation rate of the leaky wave as the beam is scanned to broadside. By nearly eliminating this stopband behavior, the double-strip leaky-wave antenna can scan from backward end fire to forward end fire without any large frequency regions of high attenuation. An approximate design rule for the double-strip antenna is discussed, and results are presented to show how the antenna may be further optimized to achieve the minimum possible variation in attenuation as the beam is scanned through broadside. Although the stopband behavior is never completely eliminated with the addition of the extra strip, the optimum design shows an almost negligible region of rapidly varying attenuation near broadside     

非子午绕组偏转器磁场的分析与计算

本文给出了鞍形和环形非子午绕组偏转器磁标位和特性函数的解析式.对彩色显象管和电子束曝光机等的偏转线圈设计具有实际意义.理论计算与实测结果符合良好.     

DESIGN AND PERFORMANCE OF SHAPING DEFLECTORS FOR VARIABLY SHAPED ELECTRON BEAM LITHOGRAPHY

In order to obtain uniform exposure in variably shaped electron beam lithography,the beam current density and edge resolution on the target must not change for different spotshapes and sizes.The key to the goal is the appropriate design of shaping deflectors.A linearand rotation compensation approach is presented.Values of linear and rotation compensationfactors versus the distances between electron source image and centers of deflectors are measuredon an experimental electron beam column with variable spot shaping.The experimental resultsare in good agreement with the calculated ones.     

变形电子束曝光机成形偏转器的设计和性能

在变形电子束曝光机中,为使曝光均匀必须保证靶上束斑电流密度物边缘分辨率不随束斑形状和尺寸的变化而改变。实现这一目标的关键是正确设计成形偏转器。本文讨论采用高灵敏度平行板偏转器实现成形偏转时,为达到上述目标应进行的线性补偿和旋转补偿的设计计算方法。给出了用实验方法改变电子源象与偏转板几何中心的轴向距离所测得的线性补偿因子和旋转补偿因子的值。实验结果与计算值符合较好。     

High-speed electrooptic deflector and its application to picosecondpulse generation

New types of electrooptic deflectors with high speed and high efficiency, which are useful for ultrafast optical switching and ultrashort optical pulse generation, are described. These deflectors are driven by an X-band standing wave along the microstrip line on an electrooptic crystal. A time-varying spatial slope of the refractive index is induced in the crystal by the electric standing wave. As a result, the ultrafast deflection is carried out. The operation of such deflectors constructed on a LiTaO₃ crystal using a 514.5-nm CW argon laser and a 9.35-GHz driving frequency was confirmed experimentally. In addition, the optical pulse compression from CW to 9.35 GHz, 16 ps was carried out with a diffraction grating, and picking out the 18.7-GHz, 8-ps pulse train was also carried out using a slit as a temporal window     

Design and simulation of waveguide electrooptic beam deflectors

Numerical simulation based on the scalar beam propagation method, was used to investigate the performance of waveguide electrooptic beam deflectors. The deflectors under investigation consist of a stack of electrooptically controlled prisms in a waveguide. The results were compared to earlier simplified analysis. It was found that for given overall device dimensions, the number of interfaces between prisms in a prism-type electrooptic deflector has significant influence on the device performance when it is small. To avoid wavefront distortion, unwanted reflection from the interfaces, and asymmetry in the deflection angles caused by small number of interfaces, one should use more than about ten interfaces in a typical deflector. Additional insights of device operation and design issues are discussed     

Scanning Polymeric Waveguide Design of a 2-D Display System

Many small-scale display systems used in head-mounted displays (HMDs) create planar images by beaming light from an optical fiber onto deflectable or rotating mirrors. This mirror-based approach has a critical limitation: the hardware of mirror scanners and grating deflectors must be significantly larger than the light beam diameter to avoid undesirable clipping or diffraction effects. Typically, attempting to reduce the size of a conventional display device reduces pixel count by loss of resolution or field-of-view (FOV) of the device. In this paper, we propose a HMD system utilizing a microfabricated 2D optical scanner controlled by a field-programmable gate array (FPGA) that overcomes the size limitations of other systems while maintaining high resolution.     

采用一级束控的声光偏转器

报道采用一级束控的声光偏转器，其带宽和衍射效率均明显优于传统器件结构的实验结果。它是高频宽带声光偏转器件发展采取的合理途径。     

Control Schemes for Driving Electro-optic Array Beam Deflectors

The beam deflectors based on electro-optic phased array（EOPA） is mainly described, and then an analysis on existing control schemes for driving the EOPA beam deflectors, based on custom hard-wired electronics or based on software in a microcontroUer, is made. Compared with these, a driving and control system for a multi-channel EOPA beam deflector is presented, in which the control assignment is implemented with a field programmable gate array（FPGA） chip. For different performance requirements, two control schemes, one with the serial scheme and another with the parallel scheme, have been explored and rapidly prototyped in Xilinx FPGA chips. With the control structures for the EOPA beam deflector, scanning rates of 588 kHz and 5 MHz can be respectivelv reached.     

基于高斯光束耦合模型的FFP性能分析

反衬度、反射率、自由光谱带宽是FFP干涉仪的重要性能指标,而FFP腔光波几何衰减因子、端面反射率及腔长3个参数又是影响这些指标的主要因素。针对以均匀光束耦合模型为基础的FFP几何衰减因子的不足,提出了以高斯光束耦合为基础的衰减因子模型,得到了与实际值接近的衰减因子公式;分析了FFP腔长和两端面反射率对反射谱反衬度及反射率的影响;根据以上分析设计了光纤光栅FFP波长解调器。     

电子束聚焦偏转系统中透镜和偏转器不对中装配误差效应的数值计算

本文讨论了透镜和偏转器在电子束系统中不对中装配造成的电子光学性质影响的数值计算问题,包括推导出不对中的透镜和偏转器在系统中的电磁场表示式,电子轨迹方程及象差积分式等。根据这些公式所编制的计算机程序已用来计算了若干个实例,从中可见不对中误差效应的数值计算对于设计和装配电子束聚焦偏转系统起到指导性的作用。     

ANALYSIS AND COMPUTATION OF THE MAGNETIC FIELD PRODUCED BY NON-RADIAL DEFLECTORS

Analytical expressions are given for computing the magnetic potential and charac-teristic functions produced by the non-radial deflectors.These expressions are useful for designingthe defiectors such as those used in the color picture tubes and the electron beam lithographysystem.The computing results are in agreement with the measured values.     

Analysis of millimeter wave phase shifters coupled to a fixedperiodic structure

The propagation characteristics of an active plasma-induced millimeter wave phase shifter coupled to a fixed periodic structure are discussed. The numerical calculation is based on an improved boundary value solution. Like a normal dielectric slab waveguide with a plasma layer, the grating waveguide displays a phase shift with the increase of the plasma density. This phase shift due to the significant change of the field distribution has an impact on the modal attenuation coefficient. It results in the scanning of the radiation beam in the vicinity of the second Bragg, Especially, at both weak and strong plasma densities when the mode losses are small, the resonances caused by the periodic structure do not appear to be weakened. The results can be used to design electronically controllable millimeter wave scanning antennas     

Circular grating coupled DBR laser with integrated focusing outcoupler

We report on the fabrication and operation of a circular grating coupled, AlGaAs-InGaAs surface-emitting distributed Bragg reflector (DBR) SQW laser with an integrated focusing outcoupler. Electron beam lithography and reactive ion beam etching were used to fabricate the laser with a first-order resonant grating for optical feedback and a separate detuned, chirped second-order grating for outcoupling and focusing the beam.     

用二维正弦相位光栅实现阵列激光相干并束

相干并束是获得高功率激光束的一种有效方法,特殊设计的二维正弦相位光栅是一种较好的并束元件。介绍了二维正弦相位光栅并束的设计方案,计算表明,在3×3和4×4分束时分束效率分别为81.1%和73.1%,与常用的达曼光栅相比分别提高37%和26.9%。对正弦相位光栅的制作和误差分析表明,并束效率存在极大值,给光栅的制作带来较大的误差宽容度,分束与并束在光栅表面的光场存在一定差别。如果仅用于并束,并束效率还有提高的可能。     

有限尺寸光栅压缩器的优化设计

分析了超短超强激光系统中有限尺寸光栅压缩器设计的关键物理参数及约束条件,得到了压缩器优化的三项基本变量。给出了一种输出能量最大化的压缩器优化方法,进而确定了有限尺寸光栅压缩器的最大工作能力。针对传统的圆光束方案提出了改进的椭圆光束方案,增大了聚焦能量,减小了焦斑尺寸,提高了峰值聚焦功率密度。通过数值模拟对500 mm曝光口径介质膜光栅在圆光束和椭圆光束两种方案下的最大输出能力进行分析比较,指出单块光栅在椭圆光束方案下可以实现500 fs,500 J,1 PW的脉冲输出。