Ionic liquid-induced synthesis of selenium nanoparticles

A simple wet chemical method has been used to synthesize selenium nanoparticles by the reaction of ionic liquid with sodium selenosulphate, a selenium precursor, in the presence of polyvinyl alcohol stabilizer, in aqueous medium. The method is capable of producing spherical selenium nanoparticles in the size range of 76-150 nm under ambient conditions. This is a first report on the production of nano-selenium assisted by an ionic liquid. The synthesized nanoparticles can be separated easily from the aqueous sol by a high-speed centrifuge machine, and can be re-dispersed in an aqueous medium. The synthesized selenium nanoparticles have been characterized by X-ray diffraction, energy dispersive X-ray analysis, differential scanning calorimetry and transmission electron microscopy techniques.     

Chirping techniques for enhancing the performance of SOA-based UWB over fiber systems: An experimental demonstration

A phaser-based processing technique was adopted in an UWB over fiber system employing SOA. The target is to simultaneously reduce the ASE noise impact and nonlinear effects inherent to optical amplification. Experimental results prove the effectiveness of chirping in terms of cross correlation and bit error rate.     

Thermal Effects and Small Signal Modulation of 1.3-μm InAs/GaAs Self-Assembled Quantum-Dot Lasers

We investigate the influence of thermal effects on the high-speed performance of 1.3-μm InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization.     

Iron oxide (n-Fe2O3) nanowire films and carbon modified (CM)-n-Fe2O3 thin films for hydrogen production by photosplitting of water

Iron oxide n-Fe₂O₃ nanowire photoelectrodes were synthesized by thermal oxidation of Fe metal sheet (Alfa Co. 0.25 mm thick) in an electric oven then tested for their photoactivity. The photoresponse of the n-Fe₂O₃ nanowires was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which is proportional to photocurrent density, J_p. The optimized electric oven-made n-Fe₂O₃ nanowire photoelectrodes showed photocurrent densities of 1.46 mA cm⁻² at measured potential of 0.1 V/SCE at illumination intensity of 100 mW cm⁻² from a Solar simulator with a global AM 1.5 filter. For the optimized carbon modified (CM)-n-TiO₂ synthesized by thermal flame oxidation the photocurrent density for water splitting was found to increase by two fold to 3.0 mA cm⁻² measured at the same measured potential and the illumination intensity. The carbon modified (CM)-n-Fe₂O₃ electrode showed a shift of the open circuit potential by −100 mV/SCE compared to undoped n-Fe₂O₃ nanowires. A maximum photoconversion efficiency of 2.3% at applied potential of 0.5 V/E_aoc was found for CM-n-Fe₂O₃ compared to 1.69% for n-Fe₂O₃ nanowires at higher applied potential of 0.7 V/E_aoc. These CM-n- Fe₂O₃ and n- Fe₂O₃ nanowires thin films were characterized using photocurrent density measurements under monochromatic light illumination, UV-Vis spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM).     

高功率非对称大光腔半导体激光器的研制

研制了高功率非对称大光腔半导体激光器。脉冲阈值电流为4-5A,在工作电流为4倍阈值时,激光器单面输出峰值功率为10-12W,其灾变功率大于20W;得到了对称的远场光强分布;器件工作寿命大于1000小时。     

半导体致冷电对金属化层粘接强度的研究

试验研究了三种半导体致冷电对金属化系统的拉伸强度，其中铋－镍－锡金属化系统与半导体致冷材料粘接强度最高，超过原始棒状材料的拉伸强度，它是半导体致冷器电对的最好的金属化系统。     

GaAs半导体脉冲激光器的激励源

本文阐述了GaAs半导体脉冲激光器的电气特性及对激励源的要求。给出了较成熟的GaAs半导体脉冲激光器的激励源,并介绍了该激励源的工作原理。     

零禁带半导体的介电常数和电子与有极声子的耦合

本文导出在零温度条件下的零禁带半导体的介电常数的解析公式。考虑到LO声子散射的贡献说明反对称的能量吸收峰。对光学声子和电子载流子之间的耦合也作了研究,产生的新的模是声子和电子激发的很强的混合,并讨论了这些模的一些特征。     

LED芯片激发荧光粉合成白光照明光源显色性的控制

光通量、色温和显色性是光源的三大重要指标。半导体LED从指示、显示应用过渡到照明应用．产品的显色性控制和评价是一个新的课题。本文应用光源显色性原理分析影响产品显色性的因素，并通过相关的试验，探讨如何通过材料选型和工艺措施，控制由蓝光LED激发荧光粉合成白光LED的显色性．使之达到预定指标。     

基于TEC的大功率LD恒温控制系统的研究

TEC存在功率有限、制冷效率低的问题,在用于大功率半导体激光器的温度控制时,常常无法达到所需的制冷效果.通过理论研究、软件仿真和实验验证,总结和提出了根据LD热负载选择TEC的理论依据和方法,以及与之匹配的大功率散热结构的设计优化准则.经实验验证,根据此原则设计的温控系统可在环境温度-40～55℃时,对30 W的LD实现恒温控制,温控范围20～40℃,温控精度0.5℃,实验结果表明此方法可以提高系统的整体效率,在设计大功率半导体激光器温控系统时具有一定的参考价值.