高功率808nm InGaAsP—GaAs分别限制结构的半导体激光器

介绍了研究分别限制结构ＩｎＧａＡｓＰ－ＧａＡｓ半导体激光器所得到的最新成果。利用引进的俄国技术，基于量子阱结构的ＩｎＧａＡｓＰ－ＧａＡｓ激光器，可用短时间液相外延技术制造。在ＧａＡｓ衬底上制成的ＩｎＧａＡｓＰ－ＧａＡｓ分别限制结构的激光器，主要参数如下：发射波入λ＝８０８ｎｍ，阈值电流密度Ｊ＝３００Ａ／ｃｍ＾２，对于条宽ω＝１００μｍ的激光器，连续功率为１－２Ｗ。     

液相外延生长超薄有源层AlxGa1—xAs／GaAs分别限制双异质结构激…

报道超薄有源层ＡｌｘＧａ１－ｘＡｓ／ＧａＡｓ分别限制双异质结构半导体激光器的液相外延的过程。讨论了过冷度、生长温度和降温速率对生长速率的影响。扫描电镜测得生长温度为６８０℃时，ＧａＡｓ有源层厚度可低至２５－３５ｎｍ。宽接触分别限制双异结构ＬＤｓ的室温连续阈值电流密度多在７００－８００Ａ／ｃｍ＾２。     

在GaAs—Ga1—xAlxAs层状结构系统中施主束缚能的一维化计算公式

本文导出了在ＧａＡｓ－Ｇａ１－ｘＡｌｘＡｓ层状结构系统中，计算施工主束缚能的一维化公式。     

Ar—HF体系的结构,性质和分析势能函数

利用Ｇａｕｓｓｉａｎ９２程序和ＣＩＤ／６—３１１Ｇ＊方法优化得到ＡｒＨＦ和ＡｒＦＨ两种线性平衡结构，计算出了这两种弱结合分子的结构参数和离解能，并使用该程序和ＭＰ２／６—３１１Ｇ＊方法计算得到它们的力常数。在此基础上，利用多体项展式方法导出ＡｒＨＦ（Ｘ１Σ＋）体系的分析势能函数，得到的势能面正确地再现了ＡｒＨＦ和ＡｒＦＨ两种线性结构，预测出ＡｒＨＦ有Ｃｓ结构存在。     

SCH量子阱激光器的光学限制特性

通过对描述半导体激光器基本光波导方程的数值求解，分析了ＡｌＧａＡｓ／ＧａＡｓ分别限制量子阱激光器的光学限制特性，比较了不同缓变结构及多量子阱结构的光学限制因子。     

液相外延生长超薄有源层Al_xGa_（1－x）As／GaAs分别限制双异质结构激光器

报道超薄有源层ＡｌｘＧａ１－ｘＡＳ／ＧａＡｓ分别限制双异质结构半导体激光器的液相外延的过程。讨论了过冷度、生长温度和降温速率等对生长速率的影响。扫描电镜测得生长温度为６８０℃时，ＧａＡｓ有源层厚度可低至２５～３５ｎｍ。宽接触分别限制双异质结构ＬＤｓ的室温连续阈值电流密度多在７００～８００Ａ／ｃｍ２。     

产生1．3μm辐射的InAsP量子势阱

产生１．３μｍ辐射的ＩｎＡｓＰ量子势阱日本Ｆｕｒｕｋａｗａ电气工业公司和光电技术研究公司合作研制成功１．３ｕｒｎ激光器。此激光器采用ＪｎＡｓＰ而不是采用ＧａｌｎＡｓＰ或ＧａｌｄｅＰ作为加载层量子势价结构中的激活区。与普通材料相比，ＩｎＡＳＰ结构的晶体...     

1．55μm InGaAsP／InP应变量子阱激光器的LP－MOCVD生长

本文首次报导了生长温度为５５０℃，以三甲基镓（ＴＭＧａ）和三甲基铟（ＴＭＩｎ）为Ⅲ族源，用低压金属有机物气相沉积（ＬＦＭＯＣＶＤ〕技术，高质量１．６２ｕｍ和１．３ｕｍＩｎＧａＡｓＰ及Ｉｎ０．５７Ｇａ０．４３Ａｓ０．９８Ｐ０．０４／Ｉｎ０．７３Ｇａ０．２７Ａｓ０．６Ｐ０．４量子阶结构的生长，并给出了１．５５ｕｍＧａＡｓＰ／ＩｎＰ分别限制应变量子阱结构激光器的生长条件，激光器于室温下脉冲激射，其阈值电流密度为２．４ｋＡ／ｃｍ２。     

Zn／GaAs（110）系统的表面驰豫及其对费密能级钉扎的影响

在紧束缚近似下，利用自洽总能计算给出了Ｚｎ／ＧａＡｓ（１１０）系统的表面几何结构。证明了低覆盖下Ｚｎ／ＧａＡｓ（１１０）表面驰豫是一普遍现象，它对准确地描述费密能级钉扎位置十分重要。进一步给出了与其它元素吸附和清洁ＧａＡｓｄ（１１０）表面的理论与实验结果之比较。     

GaAlAs／GaAs量子阱结构的实验研究

利用分子束外延生长法生长出了ＧａＡｌＡｓ／ＧａＡｓ梯度折射率分别限制单量子阱结构材料，对样品进行了光荧光谱、双晶Ｘ射线衍射和电化学电容－电压分布测量。实验结果表明，样品质量达到了设计要求，利用该材料制作的激光二极管获得了初步结果。     

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.