红光InAlAs量子点的结构和光学性质

利用ＭＢＥ方法在（００１）衬底上成功地生长密度大、尺寸小、发红光的ＩｎＡｌＡｓ／ＡｌＧａＡｓ量子点结构。通过原子力显微镜观察表明,ＩｎＡｌＡｓ量子的密度和大小都随覆盖厚度的增加而增大;发现Ａｌ原子的表面迁移率决定ＩｎＡｌＡｓ量子点的形貌,光荧光谱证实了量子点的发光峰值在红光范围,并结合形貌的统计得到了量子点的发光峰展宽主要昌受量子点的横向尺寸影响。     

退火及铟含量对InGaAs量子点光学特性的影响

研究了退火条件和 Ｉｎ 组份对分子束外延生长的 Ｉｎ Ｇａ Ａｓ 量子点（分别以 Ｇａ Ａｓ或 Ａｌ Ｇａ Ａｓ 为基体）光学特性的影响。表明：量子点中 Ｉｎ 含量的增加将导致载流子的定域能增加和基态与激发态之间的能量间隔增大。采用垂直耦合的量子点及宽能带的 Ａｌ Ｇａ Ａｓ 基体可增强材料的热稳定性。以 Ａｌ Ｇａ Ａｓ 为基体的 Ｉｎ Ｇａ Ａｓ 量子点,高温后退火工艺 （ Ｔ＝ ８３０℃）可改善低温生长的 Ａｌ Ｇａ Ａｓ 层的质量,从而改善量子点激光器材料的质量。     

垂直电子耦合InGaAs量子吉的光学特性

报导了ＩｎＧａＡｓ／ＧａＡｓ和ＩｎＧａＡｓ／ＡｌＧａＡｓ垂直耦合量子结在注入式激光器的制备工艺及其光致荧光谱，量热吸收谱和电致荧光谱的特性，该激光器的连续波波发光功率在室温下可达１Ｗ。     

自组织InAs／GaAs量子垂直排列生长研究

利用自组织生长ＩｎＡｓ／ＧａＡｓ量子点的垂直相关排列机制，生长了上下两层用６．５ｎｍＧａＡｓ间隔的ＩｎＡｓ结构、下层以ＩｎＡｓ已经成岛，由于应力传递效应，上层ＩｎＡｓ由二维生长向三维成岛生长的转变提前发生，临界厚度从１．７ＭＬ变成１．５ＭＬ，透射业微镜截面象显示形成上下两层高度差别很大的ＩｎＡｓ量子点，但是由于两层量子点之间存在器存在强烈的电子耦合，光致发光谱中只有与含大量子点的ＩｎＡｓ层相对应的     

Be掺杂InAs自组织量子点的发光特性

首次细致地研究了InAs量子点中直接掺杂Be对其发光特性的影响.光致发光(PL)谱的研究表明, 较低掺杂浓度时, 发光峰蓝移, 同时伴随着发光谱线变窄.而较高浓度的掺杂会对量子点的光谱特性产生不良的影响, 发光强度明显变弱.相信该研究对InAs自组织量子点在器件应用方面有很重要的意义.     

汽─液─固相法生长GaAs／InAs量子点

汽─液─固相法生长ＧａＡｓ／ＩｎＡｓ量子点１９９５年４月，日本《固体物理》第３０卷第３９９页发表的比留间健之等的文章介绍了汽－液－固相法生长的ＧａＡｓ／ＩｎＡｓ量子点及其光荧光蓝移现象。在以Ａｓ终止的ＧａＡｓ（１１１）面上真空蒸发约１ｎｍ的Ａｕ膜，加...     

红光量子点掺杂PVK体系的发光特性研究

无热处理制备了红光CdSe/ZnS量子点掺杂PVK的ITO/PVK:QDs/Alq3/Al结构电致发光器件.测试器件的发光光谱和电学特性等,研究了掺杂浓度(质量分数)对体系发光特性的影响,将非掺杂与掺杂体系做了比较,提出了优化掺杂体系的一些可行方案.量子点掺杂浓度较低时,主要为Alq3的发光;掺杂浓度为20%时,Alq3的发光得到抑制,红光发射最佳;继续增大掺杂浓度,QDs发光峰发生微弱红移,器件性能变差.与非掺杂体系相比,掺杂浓度合适的PVK:QDs体系大大提高了器件的稳定性.     

Mn掺杂Zn-In-S量子点的制备及发光性质研究

制备了Mn掺杂Zn-In-S量子点并研究了Zn/In的量比和反应温度对其发光性质的影响。在Mn掺杂的Zn-In-S量子点的发光谱中观测到一个600 nm发光带。通过改变Zn/In的量比,掺杂量子点的吸收带隙可从3.76 e V(330 nm)调谐到2.82 e V(440 nm),但600 nm发光峰的波长只有略微移动。这些掺杂量子点的最长荧光寿命为2.14 ms。当反应温度从200℃增加到230℃时,掺杂量子点的发光强度增加并达到最大值;而继续升高温度至260℃时,发光强度迅速减弱。此外,测量了Mn掺杂Zn-In-S量子点的变温发光光谱。发现随着温度的升高,发光峰位发生蓝移,发光强度明显下降。分析认为,Mn掺杂Zn-In-S量子点的600 nm发光来自于Mn2+离子的4T1和6A1之间的辐射复合。     

1．55μmInGaAsP及其相应量子阱结构的LP－MOCVD生长

本文研究了用低压金属有机化合物汽相外延（ＬＰ－ＭＯＣＶＤ）技术在（１００）ＩｎＰ衬底上生长ＩｎＧａＡｓｐ体材料及ＩｎＧａＡＰ／ＩｎＰ量子阱结构材料的生长条件。三甲基镓（ＴＭ６３）、三甲基铟（ＴＭｈ）和纯的砷烷（Ａ８Ｈ３）、磷烷（ＰＨ３）分别用作Ⅲ族和Ⅴ族源，在非故意掺杂情况下，ＩｎＧａＡｓＰ材料的载流子浓度为３．６×１０１５ｃｍ－３；在液氦温度和室温下，与ＩｎＰ晶格匹配的ＩｎＧａＡｓＰ光致发光半峰宽分别为１９．２ｍｅＶ和６３ｍｅＶ；对外延层的组分及厚度均匀性分别进行了转靶Ｘ光衍射仪，低温光致发光和扫描电子显微镜分析，对不同阱宽的量子阱结构材料测出了由于量子尺寸效应导致光致发光波长随阱宽增加而红移现象。     

δ掺杂的赝形高电子迁移率晶体管AlGaAs／InGaAs／GaAs结构中的费密…

报道δ掺杂赝形高电子迁移率晶体管结构Ａｌ０．３０Ｇａ０．７０Ａｓ／Ｉｎ０．１５Ｇａ０．８５Ａｓ／ＧａＡｓ的光致发光光谱研究的实验结果，除了观察到ｎ＝１电子子带到ｍ＝１重空穴子带，ｎ＝２电子子带到ｎ＝１重空穴子带间的强发光峰，还观察到了ｎ＝１电子子带到ｎ＝１轻空穴子带的弱发光峰，通过变化掺杂浓度来改变费密能级的位置，在这种δ掺杂的ＨＥＭＴｓ的系统中观察了费密边奇异性，并把它归结为费密海与费密边附近未     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.