Polarization-dependent carrier dynamics in a passive InAs/InP quantum dot waveguide

We investigate carrier dynamics in a passive InAs/InP quantum dot (QD) waveguide using 255 fs optical pulses at a central wavelength of 1568 nm. We observe strong anisotropy of absorption saturation for different polarizations. Pump-probe measurements indicate the presence of carrier relaxation dynamics on a timescale in the order of tens of picoseconds due to cascaded relaxation of carriers generated by two-photon absorption (TPA) from the bulk region to the QDs via the wetting layer. These relaxation timescales are much longer than in QD amplifiers. Our observations are supported by a rate-equation model which includes TPA, showing good agreement with the pump-probe measurements.     

非线性光学及其若干新进展

扼要介绍了非线性光学的基本概念及其最近10年来在飞秒激光，半导体材料，光纤通信和光信息存储等若干方面的研究进展。     

动态场空间分布实时测量装置的研究

描述了一套多路动态场空间分布实时测量系统，该系统是一套以微要为中心的数字化系统，可实现多路动态场空间分面睥精神病时测量。系统由微机、TMS320C50板、开关电路、检波器、传感器、放大器等设备构成硬件系统，并通过编制C50板嵌入式软件和微机主控程序实现系统功能。     

空间光学遥感器主镜加工过程中疲劳寿命研究

针对空间光学遥感器主镜镜面加工过程中,磨盘与主镜间磨削动作往复运行引起的主镜柔性支撑结构疲劳寿命问题,通过建立主镜组件的有限元模型,利用MSC.Fatigue软件按应力-寿命(S-N)法对主镜组件进行了疲劳寿命分析,确定了支撑结构的薄弱部位,并对仿真过程进行了误差分析,讨论了影响仿真结果的各个因素.对比热真空试验和动力学试验前后主镜镜面面型数据,验证了支撑结构加工、设计参量的合理性.通过疲劳寿命仿真分析,可以有效预示光学结构在加工过程中的疲劳情况,为空间光学遥感器结构的设计、加工提供理论依据和参考.     

Continuous-wave and Q-switched Operation of a Tm,Ho:YAP ring laser

We demonstrated continuous-wave (CW) and Q-switched operation of a Tm,Ho:YAP ring laser at 77 K. The maximum CW output power of 2 W at 2130.7 nm was obtained under the incident pump power of 12 W, corresponding to a slope efficiency of 23% and an optical-to-optical efficiency of 16.7%. For the Q-switched regime the maximum output energy of 5 mJ with the pulse width of 160 ns at the repetition rate of 100 Hz was achieved, corresponding to a peak power of 31.25 kW.     

Photoluminescence properties of color-tunable SrMgAl10O17:Eu2+,Mn2+ phosphors for UV LEDs

Aluminate phosphors SrMgAl₁₀O₁₇ codoped with Eu²⁺ and Mn²⁺ ions were prepared by solid-state reaction. The phase structure and photoluminescence properties of the as-prepared phosphors were characterized by powder X-ray diffraction, photoluminescence excitation and emission spectra. Upon excitation of UV light, two broad emission bands centered at 470 and 515 nm were observed, and they were assigned to Eu²⁺ and Mn²⁺ emissions, respectively. The emission color of the phosphors can be tuned from blue to cyan and finally to green by adjusting the concentration ratios of Eu²⁺ and Mn²⁺. Effective energy transfer occurs from Eu²⁺ to Mn²⁺ in the host due to the spectral overlap between the emission band of Eu²⁺ and the excitation bands of Mn²⁺. The energy transfer mechanism was demonstrated to be electric dipole–quadrupole interaction. The energy transfer efficiency and critical distance were also calculated. The phosphors exhibit strong absorption in near UV spectral region and therefore they are potentially useful as UV-convertible phosphors for white LEDs.     

Effects of controllable process factors on Al rear surface bumps in Si solar cells

High efficiency solar cells require good back surface field passivation and high back reflectance in the rear Al region. In module processes, wafer-based solar cell can break through stress during soldering uneven rear aluminum surfaces - a serious problem that affects throughput. This work examined rear surfaces with respect to controllable process factors such as ramping and cooling rates during rapid thermal processing, and the fineness of aluminum powder used in the screen-printed paste. A faster ramp up rate resulted in a uniform temperature gradient between the aluminum and silicon surfaces. As a results, the bumps on the aluminum surface were small and of high density. Fine aluminum metal powder in the paste for screen-printing contact points resulted in large distribution, high density bumps. Bumps formed during cooling in metallization, their sizes and densities were dependent the on uniformity of the aluminum and silicon liquid wetting of the silicon surface.     

极化诱导实现AlGaN薄膜材料中的超高电子浓度(1020cm-3)掺杂

材料的载流子浓度和迁移率是影响器件性能的关键因素, 变温Hall测试结果证明杂质掺杂AlGaN中的载流子浓度和迁移率随温度 降低而减小.然而极化诱导掺杂的载流子浓度和迁移率不受温度变化的影响.以准绝缘 的GaN体材料作为衬底, 在组分分层渐变的AlGaN中实现的极化诱导掺杂浓度 仅仅在10¹⁷ cm^-3数量级甚至更低. 本研究采用载流子浓度为10¹⁶ cm^-3量级的非有意n型掺杂GaN模板为衬底, 用极化诱导掺杂技术在分子束外延生长的AlGaN薄膜材料中实现了高 达10²⁰ cm^-3 量级的超高电子浓度. 准绝缘的体材GaN半导体作衬底时, 只有表面自由电子作为极化掺杂源, 而非有意掺杂的GaN模板衬底除了提供表面自由电子外,还能为极化电场 提供更多的自由电子"源", 从而实现超高载流子浓度的n型掺杂.     

真空蒸发CdSe1-xTex薄膜的光电导特性

本文采用CdSe和CdTe混合物作为真空蒸发源材料,制备了CdSe1-x、Tex(0相似文献   

小型撬装式BOG再液化装置的研发及性能测试

以最新研制的大功率回热式脉管制冷机为核心,建立了一台小型撬装式BOG(Boiled off Gas)再液化实验装置。与传统的BOG再液化装置相比,该装置具有结构紧凑、操作简单、经济效益好等优点。通过测试实验,0.4MPa时,在9400W的电机功率下,该装置制冷功率达到267W@86K;对制冷机冷头和冷屏进行改进后,在8450W的电机功率下,该装置在0.3MPa时的制冷功率达到430W@83K。实验结果表明:对制冷机冷头和冷屏进行优化后,装置的有效制冷功率大幅提高。