用于卤化铜激光器的轴向温控装置

设计并制作了一种金属筒加热器的轴向温控装置，用于典型ＣｕＢｒ激光器（电极间距５０ｃｍ，内径２ｃｍ）上使激光输出功率和效率倍增，测量了铝筒加热器温度对激光放电管外壁温度的影响。     

A vertical monolithical MOS thyristor bi-directional device

In this paper, a vertical monolithical MOS thyristor bi-directional device having all the main power electrodes and the MOS control gate electrodes on one side of the wafer is proposed. Its operating modes are described and verified by qualitative two dimensional numerical simulations. This device has a vertical current conduction ability which enables it to conduct high currents and it can block high voltages. Moreover, the fact that all the main power electrodes and the MOS control gate electrodes are on the upper side of the silicon wafer allows to overcome the packaging constraints encountered in some of the proposed, in the state of the art, vertical bi-directional MOS controlled devices.     

The MGBT: a new MOS-gated power bipolar transistor

A new device called the MGBT is described in which the upper regions of the device structure are conductivity-modulated by a positive feedback mechanism to give a lower on-state voltage drop compared to a power DMOSFET while having fast switching and fully gate-controlled characteristics. In the MGBT, a P⁺ injector coupled to the drain potential by a vertical driver DMOSFET in an emitter-switched configuration is used to inject holes which is then diverted to the entire surface region of the device by a novel cell design. 750 V MGBT devices fabricated along with DMOSFET devices on the same wafer showed 33% improvement in current density at room temperature and 46% improvement at 75°C at a forward drop of 3.5 V. The turn-off time of the MGBT was 80 ns equal to that of the DMOSFET     

顺序放电高重复频率TEA CO2激光器

研制了一台高重复频率顺序放电TEA CO2激光器,由共用光学谐振腔的两节相同放电组件组成,单组件的有效增益体积为2.5 cm×2.5 cm×55 cm.激光器允许以不同的双脉冲时间间隔和不同的脉冲重复频率工作并产生高峰值功率输出双脉冲.当两组件以200 Hz重复频率同步放电时,激光器输出平均功率为1.1 kW;当两组件以400 Hz重复频率顺序放电时,输出平均功率为550 W,双脉冲时间间隔为2.5 ms.在同一脉冲重复频率下,激光器的平均输出功率随双脉冲间隔的增大而减小.实验还测量了不同双脉冲间隔下,激光器的输出双脉冲波形.     

Thermal field created by an irradiator with a slot capacitance studied on tissue-equivalent phantoms

Experiments were carried out on phantoms imitating muscular and fatty tissues which were exposed to a single action of microwave hyperthermia in microwave set "Volna-2" (460 MHz installation with a modified antenna. The temperature in the phantoms was measured by copper-constant thermocouples in periods of automatic switching off the microwave power. Temperature distribution in the phantoms was found to depend on the depth, exposure time and power.     

小功率连续波放电DF/HF化学激光器的功率

将SF6、O2、He3种可调气体预混合,喷入带有8个高压放电极的放电管,解离F离子,沿气流方向以亚音速喷入喉道,H2/D2由喉道上下喷入,光轴在H2/D2喷入下游1mm处。研究了连续波DF/HF激光器的多谱线输出功率与SF6、He和H2/D2的流量关系,以及混合气体中加入O2对激光器性能的影响。实现了HF最大输出功率12W,DF最大输出功率11W,连续可调,功率稳定,持续时间20min。     

Mid-infrared (8.5 /spl mu/m) semiconductor lasers operating at room temperature

The room-temperature pulsed operation of a semiconductor laser emitting at 8.5 /spl mu/m is reported. This device is an optimized vertical transition quantum cascade (QC) laser. At 300 K the peak output power from a single facet is 15 mW, and the current density at threshold is /spl sim/8 kA/cm/sup 2/. The temperature dependence of the threshold current density is described by a high T/sub 0/ (107 K) in the 200-320 K temperature range.     

Concentric-Ring and Sector-Vortex Phased-Array Applicators for Ultrasound Hyperthermia

Concentric-ring phased arrays subdivided into sectors (radial slices) can, with appropriate phasing, produce power absorption patterns useful for hyperthermia cancer therapy. The ability of a concentric-ring array to move a focal region along the central axis of the transducer is well known. Less well known is the ability of such an array to produce variable diameter annular (or ring) focal regions. Such focal rings can be effective in heating some tumors if directed around the tumor periphery. These focal rings have been produced in the past by fixed annular focus lenses, or effectively by mechanical scanning of "point" focus ultrasonic transducers. Production of these focal rings by a concentric-ring phased array has the advantage of allowing the focal ring diameter and focal length to be easily changed and scanned by phasing providing much greater heating flexibility. However, under some conditions such arrays produce very large secondary focus effects along the central axis of the amay. Concentric-ring arrays can also provide only patterns of circular symmetry. These problems can be partially solved by dividing the disk of the array into sectors. By appropriate phasing of the sectors, the intensity along the central axis can be greatly reduced. Moreover, appropriate phasing of the rings and sectors can produce patterns that are circularly asymmetric. By controlling these asymmetries, nonspherical tumors can be heated more optimally. Power absorption patterns in Iossy media for this class of applicators are analyzed numerically allowing a quantitative evaluation of both advantages and limitations of this approach. A thermal model based on the bioheat equation is also used to predict temperature distributions in volumes where important thermal parameters, particularly blood flow, are varied.     

具有抑制边缘击穿的层叠结结构的平面型InGaAs/InP盖革雪崩光电二极管的设计

通过有限元分析设计了具有抑制边缘击穿的层叠边缘结结构的平面型InGaAs/InP盖革雪崩光电二极管. 通过仔细地控制中央区域结的深度,光电二极管的击穿电压降至54.3V; 同时通过调整InP倍增层的掺杂浓度和厚度,沿器件中轴的电场分布也得到了控制. 在有源区的边缘采用层叠pn结结构有效地抑制了过早边缘击穿现象. 仿真模拟显示四层层叠结构是边缘击穿抑制效果和制造工艺复杂度的一个好的折衷方案,该结构中峰值电场强度为5.2E5kV/cm,空穴离化积分最大值为1.201. 本文提供了一种设计高性能的InGaAs/InP光子计数雪崩光电二极管的有效方法.     

具有抑制边缘击穿的层叠结结构的平面型InGaAs/InP盖革雪崩光电二极管的设计

通过有限元分析设计了具有抑制边缘击穿的层叠边缘结结构的平面型InGaAs/InP盖革雪崩光电二极管.通过仔细地控制中央区域结的深度,光电二极管的击穿电压降至54.3V;同时通过调整InP倍增层的掺杂浓度和厚度,沿器件中轴的电场分布也得到了控制.在有源区的边缘采用层叠pn结结构有效地抑制了过早边缘击穿现象.仿真模拟显示四层层叠结构是边缘击穿抑制效果和制造工艺复杂度的一个好的折衷方案,该结构中峰值电场强度为5.2×105kV/cm,空穴离化积分最大值为1.201.本文提供了一种设计高性能的InGaAs/InP光子汁数雪崩光电二极管的有效方法.     

Indium tin oxide transparent electrodes for broad-area top-emitting vertical-cavity lasers fabricated using a single lithography step

We report for the first time top-emitting buried oxide vertical cavity lasers using transparent indium tin oxide electrodes. Our process enables broad-area InAlGaAs VCSELs to be fabricated in a single lithography step, thus allowing the fast turn-around time necessary for evaluating VCSEL epitaxial materials. The ITO contacts attain a peak transmission of 96%, a specific contact resistance of 10/sup -5/ /spl Omega//spl middot/cm/sup 2/, and a sheet resistivity of 2.5/spl times/10/sup -4/ /spl Omega//spl middot/cm. Under room temperature CW pumping, the devices exhibit a minimum threshold current density of 1.2 kA/cm/sup 2/ at a wavelength of 801 mm, and have a maximum light output power of 5.2 mW.     

An implantable RF solenoid for magnetic resonance microscopy and microspectroscopy

Miniature solenoids routinely enhance small volume nuclear magnetic resonance imaging and spectroscopy; however, no such techniques exist for patients. We present an implantable microcoil for diverse clinical applications, with a microliter coil volume. The design is loosely based on implantable depth electrodes, in which a flexible tube serves as the substrate, and a metal stylet is inserted into the tube during implantation. The goal is to provide enhanced signal-to-noise ratio (SNR) of structures that are not easily accessed by surface coils. The first-generation prototype was designed for implantation up to 2 cm, and provided initial proof-of-concept for microscopy. Subsequently, we optimized the design to minimize the influence of lead inductances, and to thereby double the length of the implantable depth (4 cm). The second-generation design represents an estimated SNR improvement of over 30% as compared to the original design when extended to 4 cm. Impedance measurements indicate that the device is stable for up to 24 h in body temperature saline. We evaluated the SNR and MR-related heating of the device at 3T. The implantable microcoil can differentiate fat and water peaks, and resolve submillimeter features.     

Evaluation of shoulder movement as a command control source

The purpose of this study was to evaluate the use of scapular shoulder movement as a command control source. The focus of this study was on the evaluation of movement signals from quadriplegic subjects as well as on the processing of these signals for use as command inputs to a functional neuromuscular stimulation (FNS) hand-grasp system. The shoulder movement of three C5-level quadriplegic and nine normal subjects was studied using externally mounted two-degree-of-freedom transducers overlying the sternum and clavicles. The C5-level quadriplegic subjects tested had a considerably poorer range of motion than the normal subjects. The range of motion was greatest in elevation but was coupled with a significant component of retraction. The vertical command resolution of the quadriplegic subjects ranged from eight to 13 command levels, whereas the horizontal range contained four or fewer command levels. Normal subjects were able to produce 26 to 79 command levels along the vertical axis and 18 to 85 along the horizontal axis. Subjects were able to maintain a static command level to within several percent of their range in trials lasting from 10 to 30 s. The quadriplegic subjects performed poorly in tasks where they were required to move to a point along the horizontal or vertical central axis and then along the opposite axis. The normal subjects were readily able to perform these tasks. The interference with the command signal due to movement of the opposite extremity was significant, with a maximum error ranging between 25 and 86% along the vertical axis and between 38 and 105% along the horizontal axis. Rise time and normalized velocity (velocity divided by the size of the movement) were found to be suitable for distinguishing different types of shoulder movements independent of the size of the movement. Shoulder movement in quadriplegics is suitable as a command control source for a FNS hand-grasp system requiring one proportional command signal and at least one logical command signal with appropriate processing of the signals. The available transducers are cosmetically acceptable and are easy to don and doff. Use of shoulder movement as a command control source does not interfere with other activities of the user such as eating or talking. Shoulder movement also provides a command control source that is easy for the user to learn and provides some feedback to the user through shoulder proprioception.     

The Performance of a New Direct Contact Applicator for Microwave Diathermy

A direct contact applicator, specifically designed for microwave diathermy at the Industrial, Scientific Medical (ISM) frequency of 2.45 GHz was evaluated by studying near-field patterns in free space, thermographic heating patterns in phantoms of simulated fat and muscle tissue, and associated leakage radiation. The main features are a circular waveguide with a short conical flare horn output section surrounded by an annular choke and two sets of dual posts to generate far-field circular polarization. The significant near field components of the therapeutic beam are in a transverse plane, parallel to the aperture. Heating patterns on the exposed surface of muscle phantoms and inside fat-muscle phantoms are spatially similar and relatively uniform. The leakage level is 0.8 mW/cm/sup 2/ per 100 W of forward power for direct contact and 4 mW/cm/sup 2/ per 100 W of forward power for a 1-cm air gap between aperture and planar phantoms. The uncertainty of these leakage measurements is /spl plusmn/2 dB. This investigation demonstrates the technical feasibility of a safe and effective direct contact microwave diathermy applicator operating at 2.45 GHz. The applicator is a viable candidate for hyperthermia appllications.     

垂直靶向脉冲激光沉积制备ZnO纳米薄膜

用一种新颖的制备纳米粒子与薄膜的垂直靶向脉冲激光沉积(VTPLD)方法,在室温及空气气氛下,于玻璃基底上成功地制备出ZnO纳米薄膜.用扫描电子显微镜(SEM)和X射线衍射(XRD)仪对ZnO纳米薄膜的表面形貌和结构进行了表征,用荧光光谱仪对薄膜的光致发光(PL)性能进行了测量.结果表明,当激光功率为13 W时,沉积出的粒子大小较均匀,尺寸在40 nm左右,且粒子排列呈现出一定方向性;当激光功率为21 W时,沉积的ZnO纳米薄膜图呈现出微纳米孔的连续薄膜.在玻璃基底上沉积的ZnO纳米薄膜有一主峰对应的(002)衍射晶面,表明ZnO纳米薄膜具有良好的c轴取向性.不同激光功率下沉积ZnO纳米薄膜经500 ℃热处理后的PL峰,其强度随激光能量而变化,最大发光波长位于412 nm.     

Detection of vesicoureteral reflux using microwave radiometry-system characterization with tissue phantoms

Microwave (MW) radiometry is proposed for passive monitoring of kidney temperature to detect vesicoureteral reflux (VUR) of urine that is externally heated by a MW hyperthermia device and thereafter reflows from the bladder to kidneys during reflux. Here, we characterize in tissue-mimicking phantoms the performance of a 1.375 GHz radiometry system connected to an electromagnetically (EM) shielded microstrip log spiral antenna optimized for VUR detection. Phantom EM properties are characterized using a coaxial dielectric probe and network analyzer (NA). Power reflection and receive patterns of the antenna are measured in layered tissue phantom. Receiver spectral measurements are used to assess EM shielding provided by a metal cup surrounding the antenna. Radiometer and fiberoptic temperature data are recorded for varying volumes (10-30 mL) and temperaturesg (40-46°C) of the urine phantom at 35 mm depth surrounded by 36.5°C muscle phantom. Directional receive pattern with about 5% power spectral density at 35 mm target depth and better than -10 dB return loss from tissue load are measured for the antenna. Antenna measurements demonstrate no deterioration in power reception and effective EM shielding in the presence of the metal cup. Radiometry power measurements are in excellent agreement with the temperature of the kidney phantom. Laboratory testing of the radiometry system in temperature-controlled phantoms supports the feasibility of passive kidney thermometry for VUR detection.     

An InGaAs-GaAs vertical-cavity surface-emitting laser grown on GaAs(311)A substrate having low threshold and stable polarization

We have fabricated an InGaAs-GaAs vertical-cavity surface-emitting laser (VCSEL) grown on a GaAs(311)A substrate by molecular beam epitaxy (MBE) and demonstrated continuous wave operation at room temperature. A threshold current density of 80 A/cm/sup 2//well and very stable polarization characteristics up to 2.7 times the threshold were achieved. The polarization state with the highest optical intensity was oriented along the [2~33] direction, which is the crystallographic axis exhibiting the maximum gain. An extinction ratio of more than 12.7 dB was obtained between two orthogonal polarization states. The high and anisotropic gain of a (311)A-oriented VCSEL will drastically improve the device performance by optimization and process engineering.     

雪崩光电器件过剩噪声分析

基于光子在雪崩光电器件内吸收位置的差异,提出过剩噪声因子在器件垂直方向的分布模型,并基于TCAD 和Matlab 仿真,验证了模型的有效性。模型考虑了光子在硅雪崩器件内不同吸收位置的过剩噪声因子,结合光子在器件深度方向的吸收比例,计算器件(器件结构由TCAD构造)的平均噪声因子水平:233 @ E=34×105 V/cm 和534 @ E=36×105 V/cm,比单独考虑光子在N中性体区吸收(过剩噪声因子:288 @ E=34×105 V/cm 和1294 @ E=36×105 V/cm)或P中性体区吸收(过剩噪声因子:221 @ E=34×105 V/cm 和379 @E=36×105 V/cm),更能反映器件的真实工作情况。     

UV‐Curable Silver Electrode for Screen‐Printed Thermoelectric Generator

Fabricating thermoelectric generators (TEGs) using the screen‐printing process has advantages, including mass production, device scalability, and system applicability. However, the thick film formed through the process typically has low film density, and reduced performance, because of the presence of pores in the film created by the vaporization of the resin during high‐temperature annealing. During the soldering process used for thermoelectric module fabrication, the printed solder infiltrates into the screen‐printed electrodes through the micropores in the electrodes, causing cracks of the electrode film and an increase in resistivity. In this paper, an ultraviolet radiation (UV)‐curable process for screen‐printed electrodes is reported. The paste for the electrodes is synthesized by mixing Ag flakes that can be cured at low temperature with a UV resin. Scanning electron microscope images show that the UV‐curing process significantly reduces pores and thereby results in a smooth‐surfaced electrode layer. The film density after crystallization is also enhanced. TEGs composed of 72 couples with UV‐curable Ag electrodes generate a high power density of ≈6.69 mW cm^?2 at a temperature difference of 25 °C; the device resistance is ≈0.75 Ω, and the figure of merit of the device is recorded to be 0.57, which is the highest among the printed TEGs.     

Simulation of polarization converter formed by poling-inducedpolymer waveguides

A polarization converter using electrooptic (EO) polymer waveguides is proposed and it is simulated by a full vectorial beam propagation method (VBPM) for anisotropic medium. First, an efficient structure of poling electrodes is proposed for the fabrication of TE-mode poling-induced waveguides in EO polymer. For given electrode structures of both TE-mode and TM-mode waveguides, poling-induced dielectric tensors are calculated by the finite-element method to provide refractive index distribution, data for VBPM simulation. It is shown numerically that the poled TE and TM mode waveguides work efficiently as the corresponding polarization filters. Then, new poling electrodes are suggested to fabricate a waveguide device formed by connecting the TE and TM mode waveguides adiabatically with a slowly varying structure. This waveguide device has the optic axis slowly rotating as one moves along the propagation direction, so that it will act as polarization converter. VBPM simulation shows that the polarization of the guided mode rotates following the optic axis distribution. Polarization conversion is demonstrated successfully with high conversion efficiency and low excess loss