基于fan4800C的正激式开关电源的设计

介绍了一种基于fan4800C的双晶正激式多路输出AC/DC的开关电源的原理与设计方法。分析了fan4800C的特性和工作原理,并给出了它的设计原理框图及具体设计过程,最后给出了该电源模块的实测波形及测试技术指标。     

使用菲涅耳透镜的太阳光抽运Nd:YAG激光器

太阳能是规模最大的可再生能源,为充分利用这一资源,太阳光直接抽运激光器是一种明智的选择。提出并搭建了采用两级会聚系统的太阳光抽运激光器系统。使用菲涅耳透镜作为大口径成像型第一级会聚系统,漫反射锥形聚光腔作为非成像型第二级会聚系统提高入射太阳光到工作物质的耦合效率。采用Nd:YAG晶体作为工作物质,获得了2.85 W的激光输出,从太阳光到激光的转换效率为0.43%。从菲涅耳透镜会聚效率、聚光腔内激光棒轴线上的功率分布等会聚系统方面和激光输出特性方面分析了该太阳光抽运激光器的性能;探讨了转换效率低的原因,并提出了相应的改进措施。     

LD泵浦8.7 kW固体热容激光器实验研究

设计了高功率固体热容激光器实验装置。采用二极管阵列泵浦Nd:GGG晶体腔内串联的方式,对激光器的输出特性进行了实验研究,得到输出平均功率8.7 kW,光光效率20%。获得了增益介质内的荧光分布,利用干涉测量法测量干涉条纹表征增益介质受热后折射率变化造成的畸变。     

A comparative study of full‐duplex relaying schemes for low latency applications

Various sectors are likely to carry a set of emerging applications while targeting a reliable communication with low latency transmission. To address this issue, upon a spectrally‐efficient transmission, this paper investigates the performance of a 1 full‐dulpex relay system and considers for that purpose, 2 basic relaying schemes, namely, the symbol‐by‐symbol transmission, i.e., amplify‐and‐forward and the block‐by‐block transmission, i.e., selective decode‐and‐forward. The conducted analysis presents an exhaustive comparison, covering both schemes, over 2 different transmission modes, i.e., the noncombining mode where the best link, direct, or relay link is decoded and the signals combining mode, where direct and relay links are combined at the receiver side. While targeting latency purpose as a necessity, simulations show a refined results of performed comparisons and reveal that amplify‐and‐forward relaying scheme is more adapted to combining mode, whereas the selective decode‐and‐forward relaying scheme is more suitable for noncombining mode.     

不同切型BaTiO3晶体二波耦合特性研究

分析了光折变晶体的电光系数对二波耦合特性的影响,二波耦合能量转移方向不仅依赖于晶体中光生载流子的电荷符号以及入射光与晶体ｃ轴的相对取向,而且依赖于晶体光系数各分量的相对大小;这种特性别明显地表现在相向二波耦合作用中。     

Injection seeding for single-mode operation in an optically pumped high-power D2O laser

Spectrally narrow, pulsed outputs consisting of almost a single mode have been obtained from an optically-pumped high-power (200kW) D₂O laser by adopting the injection seeding method, where single-mode radiation (seed pulse) from a low-power, compact D₂O laser has been injected into the main D₂O laser. Spectrally narrow outputs with high power having spectral widths as narrow as 5 MHz have been obtained, when the seed pulses with frequency tuned to one longitudinal mode of the main D₂O laser have been injected at a time sufficiently before the lasing of the main laser took place. The experimental results have been compared with those of numerical simulation modified to include the injection field with varying injection times.     

高效率LD端面抽运准连续355 nm激光器

报道了一台激光二极管（LD）端面抽运Nd：YVO₄晶体腔内倍频和腔外和频相结合的声光调Q准连续355 nm 紫外激光器。采用LD端面抽运双侧翼键合YVO₄基质的Nd：YVO₄晶体,在腔内置入Ⅰ类相位匹配的LiB₃O₅（LBO）晶体进行倍频实现1 064 nm和532 nm双波长准连续激光输出,通过消色差透镜将双波长激光聚焦耦合到Ⅱ类相位匹配的LBO 晶体中进行和频,并采用双向和频光路,获得了高效率、高光束质量、高重复频率的准连续355 nm 紫外激光输出。在抽运功率为28.6 W、重复频率为20 kHz时,355 nm激光最大输出功率4.2 W,脉宽为20.6 ns,光-光转换效率为14.7%,激光器光束质量因子M_x²和M_y²分别为1.29和1.23。     

探地雷达数值模拟中广义完全匹配层吸收边界条件的模拟分析

探讨探地雷达正演模拟中,应用广义完全匹配层(GPML)吸收边界条件时的模拟效果.利用时域有限差分(FDTD)法将麦克斯韦方程离散化,再采用Mur超吸收边界条件和GPML吸收边界条件吸收向外的电磁波,模拟充水岩溶的雷达图像;同时,采用GPML吸收边界条件模拟多个圆柱体异常模型和倾斜界面异常模型的探地雷达剖面图像.对模拟结果的分析可知,GPML吸收边界条件可有效地吸收向外的电磁波,其吸收效果优于Mur超吸收边界条件,在探地雷达的应用中可推广应用.     

注入电流对绿光高压LED光电特性的影响

设计并制备了12 V 的GaN基绿光高压发光二极管（LED）,并对其进行了变电流测试。研究了绿光高压LED的正向电压、峰值波长、光功率以及光效等重要参数随注入电流的变化关系,电流变化范围为3~50 mA,测试温度为25 ℃。实验结果表明：电流对绿光高压LED的光电特性有很大影响。在驱动电流为20 mA时,对应电压为14 V。随着注入电流的增大,峰值波长蓝移了2 nm。随着电流的增大,光功率近似于线性增加。在注入电流从3 mA增大到20 mA的过程中,光效降低了约61%;在注入电流从20 mA增大到50 mA的过程中,光效降低了约39%。这说明高压LED在大电流驱动时,光效降低的幅度比较缓慢。上述结果对 GaN基绿光高压 LED 的改进优化具有一定的参考价值。     

Compact and high-energy diode-side-pumped Q-switched Nd:YAG slab laser system for space application

We develop a compact and high-energy Nd：YAG slab laser system consisting of an oscillator and an amplifier for space applications. The oscillator is a diode-side-pumped electro-optically Q-switched slab laser with a cross-Porro resonator. The KD＊P Pockels cell with a low driving voltage of 950 V is used to polarization output coupling. The amplifier is a Nd：YAG zigzag slab pumped at bounces. The maximum output pulse energy of 341 m3 with 13 ns pulse duration is obtained from the system at the repetition rate of 20 Hz and the beam quality factors are M2=3.1 and M2=3.5. The beam pointing stabilities of the laser system are 3.05μrad in the X-direction and 3.99 grad in the Y-direction, respectively.