表面高阶曲线光栅半导体激光器横模特性分析

半导体激光器在光通信、生物医疗、激光雷达等领域中得到广泛应用,其单模稳定输出特性一直是国内外的研究热点。制备了一种基于表面高阶曲线光栅的宽脊波导半导体激光器,刻蚀曲线型高阶光栅后高阶横模损耗远大于基横模损耗,同时设置宽脊电流限制注入结构,使得高阶横模激射阈值高于基横模阈值,从而改善器件的横模特性并压窄光谱线宽。利用温控模块将器件的工作温度控制为18℃,对腔长为2 mm、条宽为500μm的器件进行测试,在0.5 A电流下测得慢轴发散角为5.3°,快轴发散角为29.2°,在1 A驱动电流下测得3 dB光谱线宽为0.173 nm,边模抑制比为22.6 dB。实验结果表明,表面高阶曲线光栅对宽脊波导半导体激光器中的高阶横模起到了抑制作用且能够压窄光谱线宽,有助于实现半导体激光器的单模稳定输出,同时器件采用紫外光刻工艺,大幅降低了器件的制备难度。     

折射率缓变波导层分别限制单量子阱半导体激光器的模式分析

本文提出一种能够精确分析波导层具有任意折射率分布而且收敛性好的分层逼近迭代法,研究了折射率缓变波导层分别限制单量子阱(GRIN-SCH-SQW)中波导层的折射率分布对近场分布,近场束宽,光限制因子,远场分布,远场角,激射阈值的作用,并与延伸抛物型近似解和折射率突变波导层分别限制单量子阱半导体激光器进行较全面的比较.结果表明:延伸抛物型近似不宜普遍采用;采用适当的缓变波导层可进一步降低阈值(例如采用抛物型或线性分布),或进一步减小远场角(例如采用倒抛物型分布).     

量子阱材料折射率低偏振相关性研究

分析了阱宽、垒高和应变对量子阱材料TE模和TM模折射率的影响,并剖析了其中的物理机理.研究表明:对于量子限制效应带来的量子阱折射率偏振相关性,阱宽越小或垒高越高,折射率偏振相关性越大.压应变增大时,折射率偏振相关性增大,张应变可以克服量子限制效应带来的折射率偏振影响.对于不同阱宽和垒高的量子阱,均存在合适的张应变量使折射率偏振相关性最小,且阱宽越小或垒高越高所需的张应变量越大.根据以上分析,提出量子阱材料折射率低偏振相关设计方法,并据此设计出C波段(1 530～1 565 nm)内折射率低偏振相关(小于0.03)的量子阱材料In0.49Ga0.51As/In0.77Ga0.23As0.5P0.5.研究结果有助于优化设计光网络中关键器件.     

多量子阱有效折射率偏振相关性研究

分析了多量子阱材料各参数对其TE模和TM模有效折射率的影响。结果表明:阱数增多,多量子阱有效折射率降低,当量子阱数目大于3时,其有效折射率的变化不明显。垒厚增加,有效折射率略有降低。存在合适的张应变量使TE模和TM模有效折射率峰值波长接近的同时,折射率差值整体最小,偏振相关性最小。据此提出多量子阱材料有效折射率低偏振相关设计方法,并设计出C波段内(1530~1565 nm)折射率低偏振相关的InGaAs/InGaAsP多量子阱材料。研究结果有助于设计实用化的有效折射率低偏振相关量子阱材料。     

混合应变多量子阱波导结构设计

本文从理论上对混合应变量子结构（既有张应变量子阱又有压应变量子阱）的光学限制因子进行了讨论。由于垒层宽度较小，其变化量也不大，对光学影响相对小一些。当各层的折射率一定时，对称和非对称结构的最佳波导层厚度差不多，限制因子与波导层厚度的关系也类似，在最佳波导层厚度附近的区域，ГＴＭ／ГＴＥ比值变化对波导层厚比较敏感，这点可以用于偏振无关放大器的设计中，因为我们能够通过调节波导层厚度改变ＴＭ／ＴＥ模式增     

高功率1060 nm半导体激光器波导结构优化

针对高功率1060 nm半导体激光器的外延结构,分析了影响器件功率进一步提高的原因.根据分析,优化了激光器的量子阱结构和波导结构,并理论模拟了波导宽度对模式和输出功率的影响.根据不同模式的光场分布,对量子阱有源区的位置进行了优化,并设计了非对称、宽波导结构.对不同模式的限制因子进行了计算,结果表明,优化后的非对称波导结构能够在降低基模的限制因子的同时,增加高阶模式的损耗.     

多孔波导小发散角量子级联激光器

本文报道了激射波长为4.5μm带有多孔结构波导的量子级联激光器,具体器件工艺首先采用电化学腐蚀方法在脊形两侧制作出树枝状多孔结构,后续步骤在其中填充入金属材料。与普通脊形器件相比,带有多孔结构的新型器件具有更好的光束质量。此种半导体-金属混合结构对高阶模光反馈吸收作用较强,可对高阶横模产生明显的抑制作用,最终实现远场发散角达4.9°的基横模激射。     

抗中子辐射加固超辐射发光二极管的研究

我们设计并制作了一种高性能的抗中子辐射的超辐射发光二极管。高能中子辐射后产生的位移损伤造成器件有源区内少子寿命减少,从而导致器件光输出功率的降低。通过理论分析可知高输出功率的超辐射发光二极管对中子辐射的敏感度较低。本文中的超辐射发光二极管的有源区采用了具有高量子效率和小体积有源区的InGaAsP/InP多量子阱结构,外延波导层采用了线性缓变折射率分别限制结构(GRIN-SCH),并设计和优化出了特殊波导吸收区和腔面减反射膜结构。辐射实验结果显示,在中子注量为6?10₁₃～1?10₁₄n/cm₂(1MeV)下,InGaAsP/InP多量子阱结构的超辐射发光二极管与双异质结结构相比具有更好的抗中子辐射性能。     

980nm InGaAs／GaAs／AlGaAs大功率LDs模式特性研究

针对目前大功率980 nm量子阱半导体激光器(LDs)为降低阈值电流而要求激射条宽窄、腐蚀深度深而造成的P-I曲线扭折、侧向模式不稳定问题采用有效折射率近似方法进行模拟分析,并得到了实验上的证实.通过采用不对称波导及双量子阱结构,制备了低阈值(19 mA)模式稳定的InGaAs/GaAs/AlGaAs LDs,其斜率效率0.6 W/A(8 μm×500 μm,未镀膜器件),在输出功率达到100 mW时保持横模、侧模的稳定.     

InGaAs/InAlAs多量子阱脊形光波导及其定向耦合器准矢量分析

运用基于三角函数展开的三维准矢量束传播法分析了由InGaAs/InAlAs多量子阱(MQW)构成的脊形光波导及其定向耦合器;获得了脊形光波导承载的模场分布及其有效折射率,并观察到了TM模的奇变;模拟了光波在定向耦合器件中的传输演变情况.所得结果为制作由此为基础的复杂器件奠定了基础.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.