Electrooptic materials for digital light beam deflectors

The technology of digital deflectors made significant progress in the past. The success of this development was primarily based on the advances made in the preparation of electrooptic materials. The selection criteria are described here for a material suitable for the particular application under consideration, and a survey is made of the most promising electrooptic materials, both solid state and liquid. The list of solid-state materials comprises representatives of the class of oxygen octahedra ferroelectrics, KDP isomorphs, and AB-type compounds. A section on Kerr liquids begins with considerations for the optimization of the molecular structure and gives experimental results on some newly synthesized materials. Further, the impurity conduction phenomena that are important to the technical performance are described in detail. The final section reviews the present state of digital deflector development.     

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     

High-frequency, stripline, multireflection electrooptic beam deflectors

A novel electrooptic (EO) beam deflector has been designed through numerical simulation. This stripline lithium tantalate device has the potential to electrooptically modulate the deflection of an optical pulse at unprecedented frequencies. Velocity matching of the optical pulse to a high-frequency transmission line signal is achieved through reflections of the fast optical pulse. An optimal design criterion is formulated for this device. Deflection capability is estimated to be 8/spl deg/. The device is intended for use in deflection-based optical analog-digital (A/D) conversion.     

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.     

Fast simulation of sigma-delta modulators using SPICE

Presents a fast simulation method using SPICE. We traded the prohibitive time-consuming simulation problem for a much less time-consuming problem, plus a little analysis work. This makes it possible for one to use SPICE simulation to optimize the parameters in the modulator within a reasonable time period. Rounding and truncation errors within the circuit simulation algorithms typically set an upper limit on the measurable SNR on the order of 90 dB. This implies that very high-resolution modulators cannot correctly be simulated by SPICE. Fortunately, 90 dB resolution is adequate for most modern communication baseband A/D converters     

Fast electron beam scanlaser

The electron beam scanlaser (EBS) is a device in which a modified electrooptic light valve is used as a mode selector in the highly degenerate flat-field conjugate laser resonator to provide a scanning light spot. This paper describes improvements in the mode selection portion of the EBS which make the device far more promising. In particular, 1) the charge storage time is now under control, and can be as short as needed, 2) the KDP is protected from the electron beam, 3) the electron gun is protected from the KDP, 4) provision can be made for the needed high-quality optical surfaces in the mode selector, and 5) the transparent conducting coating on the mode selector's KDP crystal has been removed, indicating that the insertion loss of the mode selector can be reduced to less than 1.5 percent.     

Quantum well modulators for optical beam steering applications

The authors demonstrate the possibility of laser beam control with a dynamic grating constructed of Fabry-Perot reflection modulators. Individually addressed stripes composed of quantum well reflection modulators form a diffraction grating capable of high resolution and large scanning angles. The authors obtained control of the far field pattern in the optical regime. Since the far field is a Fourier transform of the spatial reflectivity of the device, it was possible to steer a laser beam by imposing a pattern that oscillates spatially on the stripes. A simple setup results in a continuous scanning angle of 2 degrees and an output beam width of about 0.1 degrees .<>     

Digital light deflectors

Several electrooptic digital light deflection techniques have been proposed. The maximum number of resolvable deflection positions for all methods is determined, essentially, by economic reasons, the tolerable amount of background fight, and aberrations. In this paper, three different types of deflection methods (split angle, total internal reflection, Wollaston prism) are described. Design, construction details and performance of three deflector models are reported. Combined deflection systems use the advantageous properties of each of these methods to economically obtain the maximum number of resolvable deflection positions. A suggested combination to achieve 1024 × 1024 positions arranged in a two-dimensional field would consist of one total internal reflection stage, seven stages of split angles, and two stages of Wollaston prisms for each dimension.     

Fast electro-optical phase modulators completely measured in frequency and time domains

Results showing the complete linear behaviour of LiNbO/sub 3/ electro-optical phase modulators are presented. In a self-homodyne experiment the devices are investigated in the frequency and time domains at a data rate of 3.2 Gbit/s. The results of computer simulation are in good agreement with measurement results.<>     

Fast fiber-laser alignment: beam spot-size method

A novel fast and cost-effective method is introduced for the active alignment of a fiber to a laser diode: only four easy laser beam spot-size measurements are required for moving the fiber tip from the far field to the proximity of the optimal alignment position, thus dramatically reducing the total alignment time (at least five times faster than a conventional method), as experimentally confirmed. Moreover, in contrast to the existing methods, the new method is failure-proof. The principle of the proposed method can be applied generally to any type of packages and is illustrated by an example of a butterfly package.     

二极管激光器快轴光束准直

二极管激光器泵浦模块输出光束发散角小、指向精度高,但其中的快轴准直(FAC)微透镜装调工艺不能满足大功率模块的应用要求,针对此问题,分析了快轴准直微透镜的光束准直原理,简述了应用FAC透镜时的参数选择和装调问题.通过光学成像方法实时监测二极管激光巴条(bar)的近场像和远场像,对FAC透镜分别进行粗调节和细调节,获得了...     

Ultrahigh resolving electrooptic prism array light deflectors

A type of light deflector that shows ultrahigh resolving power is proposed. This light deflector consists of arrayed electrooptic prisms. The resolving power of this deflector isNtimes larger than that of a single electrooptic prism, whereNis the number of arrayed prisms. If the voltages applied on each crystal are all the same, the deflecting angle is discontinuous. But if the voltages are not equal to each other, it can be continuous. Experiments were done using a simple deflector. The experimental results agreed with the theory. The experimental deflector showed 50 resolved individual spots when maximum applied voltages were ± 600 V. It is clear that we can have a light deflector that shows over 600 resolvable spots easily. Current techniques are sufficient to manufacture such deflectors.     

MULTIPOLE ELECTROSTATIC DEFLECTORS FOR OBTAINING UNIFORM DEFLECTION FIELD

The general field solutions are presented for two kinds of infinitely long multipoleelectrostatic deflectors.A method is given to obtain uniform field near the optical axis.We calculated sixforms of deflectors,the concerned formulas and data are given.The relationship and difference between twokinds of deflectors are analysed.     

Fast detection of instability in sigma-delta modulators based on unstable embedded limit cycles

As a sequel to a previous study (Wong and Ng) on the nonlinear dynamical behavior of low-pass, high-order (order > 2), single-bit /spl Sigma//spl Delta/ modulators with distinct unit-circle noise transfer function zeros, this paper proposes a novel scheme for the fast detection of unstable operation in these modulators under general time-varying input. The scheme is based on the variation of unstable embedded limit-cycle fixed points (which form the bounds beyond which the modulator becomes unstable) versus modulator input amplitude. Deployment of the detection scheme requires simple analog components with possible simplification. The effectiveness of the scheme is demonstrated with numerical examples.     

High S/N-ratio electrooptic prism-array light deflectors

A method to construct electrooptic prism-array deflectors which is, in the author's view, the most promising device for application in digital systems is analyzed. Experiments agreed well with the analysis. An experimental deflector with nine elements showed 180 resolved individual spots when driven with a maximum voltage of ± 580 V. It is shown that this type of deflector is capable of resolving over one thousand Rayleigh points. For example, with fifty-four LiTaO3crystals with the dimension of0.2 times 0.8 times 21mm, one can have 1080 Rayleigh points for ± 64 V applied. The extinction ratio of this deflector is over 32 dB.     

快速扫描针孔法测量脉冲染料激光束直径

本文描述了一种能够快速准确地测量脉冲染料激光束直径的方法，该方法是以步进电机驱动针孔扫描，Ｂｏｘｃａｒ－ｃｏｍｐｕｔｅｒ信号处理系统做高斯拟合，精度优于５％。     

Comparison of the propagation performance over standard dispersive fiber between InP-based /spl pi/-phase-shifted and symmetrical Mach-Zehnder modulators

We estimated and experimentally verified the output phase and intensity characteristics versus the applied voltage of an InP-based Mach-Zehnder modulator from the measured data of refractive index and loss variations specific to the phase section material (Fabry-Perot method). We have then simulated the propagation performance of a Mach-Zehnder modulator taking into account the possible phase-shift between both arm of the interferometer. In total agreement with experimental results, we show that the simple single-arm modulation scheme does not require high voltages and that the /spl pi/-phase-shifted Mach-Zehnder modulator is far more convenient for a 10-Gb/s propagation over standard dispersive fiber than a symmetrical modulator.     

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.     

Fast beam propagation method for the analysis of second-ordernonlinear phenomena

We adopt an implicit scheme to solve both the dispersive/diffractive and the nonlinear step in the beam propagation method (BPM) code. Unlike the Runge-Kutta implementation used in the nonlinear part of the propagation, the totally implicit scheme is considerably fast. Transparent boundary conditions can be also applied to effectively treat radiation problems. To validate the method, numerical examples are given and results compared with analytical solutions     

Fast synthesis of aperture distributions for contoured beam reflector antennas

The use of a gradient function method to optimise aperture fields for contoured beam reflector antennas is shown to be efficient when compared with other approaches. A key feature of the method is that an analytical expression is used to modify the aperture distributions in each iteration.<>