一竞赛求值题的多种解法

在数学竞赛中,常有一元二次方程的根的代数式求值问题.这类问题,有直接的方法,就是先解此一元二次方程,然后把根代入就能求出结果;其实不解方程,也可以把值求出来.下面以一竞赛题为例,学会用多种解法解这类题目.     

整数的一个令人惊奇的性质

文〈1〉提出了整数的一个令人惊奇的性质 :对任意的一个整数 ,以你喜欢的任意方式重新排列 ,则开头的数与新的数之间的差 ,永远会被 9整除 !例如 :原数为 1 2 56 3 ,重排后的新数为 2 3 6 51 ,它们的差为 1 1 0 88,1 1 0 88÷ 9=1 2 3 2 ;原数为 3 3 3 3 3 ,重排后还是 3 3 3 3 3 ,它们的差为 0 ,0÷ 9=0 ;原数为 6 72 6 3 6 ,重排后为6 6 6 3 72 ,差为 6 2 6 4,6 2 6 4÷ 9=6 96 .以上选出的三个数都具有这个性质 ,有兴趣的话你可以任选整数进行尝试 .这个性质如果要进行严格的证明 ,似乎无从入手 .我们就先从两位数入手 .设原两位数为ａｂ…     

量子阱共振腔增强型光电探测器的高功率特性

通过测量1．55Mm量子阱共振腔增强型光电探测器的光电流随反向电压和光功率的变化关系,以及模拟能带结构、电场分布等特性,研究了量子阱共振腔增强型光电探测器的高功率特性．分析了光电流的产生机制,测量了1．064μm量子阱共振腔增强型光电探测器的光电响应,模拟了具有不同势垒高度的量子阱共振腔增强型光电探测器的光电响应．从实验和模拟两方面证明了量子阱的势垒高度是影响量子阱共振腔增强型光电探测器高功率特性的最主要因素．     

基于石墨烯的半导体光电器件研究进展

石墨烯自从被发现以来,由于其零带隙、低电导率、常温下的高电子迁移率及量子霍尔效应和独特的光吸收等优良特性,引发了世界各国科研人员的重视,研究人员对其物理性质及应用的研究越来越多并且进展迅速．本文以光纤通信用光电器件中的探测器、调制器为主,综述了石墨烯在光电探测器、调制器以及超快锁模激光器和用于发光二级管、触摸屏透明导电薄膜等方面的应用．     

1.3μm GaAs基量子点垂直腔面发射激光器结构设计与分析

结合垂直腔面发射激光器（VCSEL）原理以及量子点增益特点，计算了不同结构VCSEL的腔内损耗和量子点的模式增益.分析了激光器阈值特性以及氧化限制层对光损耗的影响.设计了含 氧化限制层的13μm量子点VCSEL结构. 关键词： 量子点 垂直腔面发射激光器 增益     

Molecular Beam Epitaxy Growth and Photoluminescence of Type-Ⅱ （GaAs1-xSbx／InyGa1-yAs）／GaAs Bilayer Quantum Well

We report a systematical study on the molecular beam epitaxy growth and optical property of (GaAs1-xSbx/InyGa1-yAs)/GaAs bilayer quantum we]] (BQW) structures. It is shown that the growth temperature of the wells and the sequence of layer growth have significant influence on the interface quality and the subsequent photoluminescence (PL) spectra. Under optimized growth conditions, three high-quality (GaAsSb0.29/In0.4 GaAs)/GaAs BQWs are successfully fabricated and a room temperature PL at 1314 nm is observed. The transition mechanism in the BQW is also discussed by photoluminescence and photoreflectance measurements. The results confirm experimentally a type-Ⅱ band alignment of the interface between the GaAsSb and InGaAs layers.     

Bolometric effect in a waveguide-integrated graphene photodetector

Graphene is an alternative material for photodetectors owing to its unique properties.These include its uniform absorption of light from ultraviolet to infrared and its ultrahigh mobility for both electrons and holes.Unfortunately,due to the low absorption of light,the photoresponsivity of graphene-based photodetectors is usually low,only a few milliamps per watt.In this letter,we fabricate a waveguide-integrated graphene photodetector.A photoresponsivity exceeding0.11 A·W ~(-1) is obtained which enables most optoelectronic applications.The dominating mechanism of photoresponse is investigated and is attributed to the photo-induced bolometric effect.Theoretical calculation shows that the bolometric photoresponsivity is 4.6 A·W ~(-1).The absorption coefficient of the device is estimated to be 0.27 dB·μm ~(-1).     

Design and fabrication of multi-channel photodetector array monolithic with arrayed waveguide grating

We have provided optical simulations of the evanescently coupled waveguide photodiodes integrated with a 13-channels AWGs. The photodiode could exhibit high internal efficiency by appropriate choice of layers geometry and refractive index. Aseamless joint structure has been designed and fabricated for integrating the output waveguides of AWGs with the evanescently coupled waveguide photodiode array. The highest simulation quantum efficiency could achieve 92% when the matching layer thickness of the PD is 120 nm and the insertion length is 2 μm. The fabricated PD with 320-nm-thick matching layer and 2-μm-length insertion matching layer present a responsivity of 0.87 A/W.     

用刻蚀坑方法抑制平面型InGaAs/InP盖革模式APD的边缘击穿

通过测量平面型InGaAs/InP雪崩光电二极管闭管扩散器件帽层InP中Zn杂质的分布,拟合出掺杂浓度随扩散深度的变化函数,并且利用离化积分研究不同倍增层厚度下的最佳刻蚀坑深度和最佳刻蚀方法.结果表明在帽层深度不变的情况下,最佳刻蚀坑深度会随着倍增层厚度而变化,当倍增层厚度为1μm左右时刻蚀坑深度在0.1~0.3μm之间.采取反应离子刻蚀可以获得良好的刻蚀坑形貌,有利于边缘击穿的抑制.     

高稳定线性调谐GaAs基波长可调谐共振腔增强型探测器

研制了一种GaAs基波长可调谐共振腔增强型探测器. 采用分子束外延设备生长In_0.25Ga_0.75As/GaAs量子阱作为器件的有源区, 无偏压时器件的响应峰波长在1071 nm,器件在21 V的直流调谐电压下,实现了波长大于23 nm的调谐. 统计结果表明,当调谐电压大于5 V时,调谐电压与响应波长之间具有稳定、精确的对应关系, 且近似线性调谐,同时对器件响应峰的特性进行了理论分析. 关键词： GaAs 共振腔增强型探测器 高稳定 线性调谐