Mode characteristics of semiconductor equilateral triangle microcavities with side length of 5-20 mu m

Semiconductor equilateral triangle microresonators (ETRs) with side length of 5, 10, and 20 mum are fabricated by the two-step inductively coupled plasma (ICP) etching technique. The mode properties of fabricated InGaAsP ETRs are investigated experimentally by photoluminescence (PL) with the pumping source of a 980-nm semiconductor laser and distinct peaks are observed in the measured PL spectra. The wavelength spacings of the distinct peaks agree very well with the theoretical longitudinal mode intervals of the fundamental transverse modes in the ETRs, which verifies that the distinct peaks are corresponding to the enhancement of resonant modes. The mode quality factors are calculated from the width of the resonant peaks of the PL spectra, which are about 100 for the ETR with side length of 20 mum.

Near infrared photoluminescence from Yb,Al Co-implanted SiO2 films on silicon

Intense room-temperature near infrared (NIR) photoluminescence (980 nm and 1032 nm) is observed from Yb,Al co-implanted SiO2 films on silicon. The optical transitions occur between the F-2(5/2) and F-2(7/2) levels of Yb3+ in SiO2. The additional Al-implantation into SiO2 films can effectively improve the concentration quenching effect of Yb3+ in SiO2. Photoluminescence exitation sprectroscopy shows that the NIR photoluminescence is due to the non-radiative energy transfer from Al-implantation-induced non-bridging oxygen hole defects in SiO2 to Yb3+ in the Yb-related luminescent complexes. It is believed that the defect-mediated luminscence of rare-earth ions in SiO2 is very effective.

980nm InGaAs/InGaAsP quantum well lasers with AlGaAs cladding grown by metal organic chemical vapour deposition

The authors report on the fabrication of 980 nm InGaAs strained quantum well lasers with hybrid materials of InGaAsP as waveguide and AlGaAs as cladding grown by metal organic chemical vapour deposition. The InGaAs/InGaAsP/AlGaAs diode lasers (100 x 800 mu m) with broadened waveguide structure exhibit a threshold current of 180 mA, a slope efficiency of 1.0 W/A, and a high characteristic temperature coefficient (T-0) of 230 K.

New color centers and photostimulated luminescence of BaFCl : Eu2+

Three new absorption bands, appearing around 670, 865 and 980 nm, are observed in BaFCl:Eu2+ phosphors. They are ascribed to F aggregates formed by association of F centers or by trapping of electrons to the primary F-n(+) (n = 2,3,4) centers. The growth curves of F and F-aggregated centers are similar and may be divided into three stages. The photostimulated luminescence (PSL) decays by stimulation into the absorption bands of F centers and of F aggregates are different; the former decay logarithmically and the latter decay hyperbolically. Some non-radiative processes related to F aggregates, such as electron migration, occur accompanying the PSL process, which may reduce the PSL efficiency and sensitivity of the phosphors. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.

The third subband population in modulation-doped InGaAs/InAlAs heterostructures

We have observed the population of the third (n=3) two-dimensional electron subband of InGaAs/ InAlAs modulation-doped structures with very dense sheet carrier density by means of Fourier transform photoluminescence (PL). Three well-resolved PL peaks centered at 0.737, 0.908, and 0.980 eV are observed, which are attributed to the recombination transitions from the lowest three electron subbands to the n=1 heavy-hole subband. The subband separations clearly exhibit the features of the stepped quantum well with triangle and square potential, consistent with numerical calculation. Thanks to the presence of the Fermi cutoff, the population ratio of these three subbands can be estimated. Temperature and excitation intensity dependence of the quantum well luminescence intensity is also analyzed. (C) 1997 American Institute of Physics.

掺镱稀土金属氧化物纳米粉体的上转换发光

：用共沉淀法合成出Yb3+离子掺杂的Y2O3 粉体，采用纳米粒度分析仪表征后，其粒径主要 分布在40～80 nm；由于Yb3+的4f13 电子易于与近邻离子发生相互作用，该粉体在波长为980 nm 的 半导体激光器激发下发射出中心波长为540 nm 的绿色上转换荧光. 由于这种材料具有上转换发光 性能以及发射光谱的红移现象，有望应用于荧光标记或者红外探测方面.

黄土丘陵区县南沟流域生态恢复的生态经济耦合过程及可持续性分析

生态恢复不但是自然和技术过程,更重要的是经济过程,生态经济耦合是生态恢复成败及能否持续的关键。综合应用经济学、能值和生态足迹分析工具,系统研究了黄土丘陵区县南沟流域生态恢复过程中的生态经济系统演变过程及其特征,旨在探索生态可持续的经济社会发展机制。结果表明,2000～2005年流域产业结构及其多样性显著改善,生产力显著提高并跨越低水平进入高水平发展阶段,农民的生活状况已经由温饱逐步迈向小康水平。基于能值的生态经济耦合分析结果显示2002～2005年流域环境负载率(ELR)下降,持续性指数(ESI)增加。生态足迹结果显示流域2000年和2005年的生态盈余分别为0.03hm2和0.239hm2,新指标万元产值生态足迹(EFprod)分别为53.5hm2/万$和33.6hm2/万$,生态压力指数(EFPI)分别为0.980和0.838,流域处于弱可持续状态。上述结果显示生态恢复提高了流域资源利用和转换效率,环境负载率下降,人类经济活动对生态生产性有效空间的占用减少,可持续性提高。研究结果表明生态恢复是黄土丘陵区实现生态经济良性耦合、协调发展的基本途径。

Near-Infrared Femtosecond Laser for Studying the Strain in Si1-xGex Alloy Films via Second-Harmonic Generation

The second-harmonic generation (SHG) from Si1-xGex alloy films has been investigated by near-infrared femtosecond laser. Recognized by s-out polarized SHG intensity versus rotational angle of sample, the crystal symmetry of the fully strained Si0.83Ge0.17 alloy is found changed from the O-h to the C-2 point group due to the inhomogeneity of the strain. Calibrated by double crystal X-ray diffraction, the strain-induced chi((2)) is estimated at 5.7 x 10(-7) esu. According to the analysis on p-in/s-out SHG, the strain-relaxed Si0.10Ge0.90 alloy film is confirmed to be not fully relaxed, and the remaining strain is quantitatively determined to be around 0.1%.

OPS-VECSEL芯片的生长与光谱研究

光泵浦半导体垂直外腔面发射激光器(OPS-VECSEL)是一种新型激光器,在很多领域都具有广阔的应用前景.采用MOCVD生长了工作波长为980 nm的VECSEL芯片,测量了芯片X射线衍射(XRD)图谱,光致发光(PL)谱和反射谱,结果表明,芯片生长的准确性较高.同时采用物理光学的理论结合实际模型,运用矩阵分析方法计算了VECSEL的反射谱,计算结果与实验结果吻合良好.最后,通过对不同窗口层厚度的纵向增强因子的计算和分析得到了共振结构具有高的峰值增强,反共振结构具有大的增益带宽.在理论上提出,对于该OPS-VECSEL结构,采用共振和反共振结构之间的窗口厚度可以使其稳定工作在特定波长而又不严格限制增益带宽.

金膜上亚波长周期性孔阵的模拟与研制

分析了980 nm波长的光在透过制作在金膜上的亚波长周期性孔阵时的透射增强现象.通过建立中心带缺陷孔的三角晶格的孔阵模型,并采用三维时域有限差分方法对该模型的透射情况进行模拟分析.结果表明通过优化孔阵周期参数可以对特定波长的光实现一定程度的选择透过性.当孔阵周期为450 nm,中心缺陷孔径为400 nm,孔阵中单个孔孔径为150 nm时,980 nm波跃光透过该孔阵时具有明显的透射增强效应,并且距孔阵表面3μm的远场光斑尺寸被局限在亚波长尺度(880 nm).研究了使用聚焦离子束在金膜上制备孔阵的工艺,成功研制了与没计尺寸一致的孔阵.这种孔阵可以集成在980 nm垂直腔面发射激光器上,用于改善器件的远场光学特性.

60%电光效率高功率激光二极管阵列

设计并制备了980 nm高量子效率和极低光损耗的激光二极管(LD)外延材料和器件。微通道封装1 cm激光二极管阵列在连续(CW)工作条件下最大电光效率达到60.0%,相应的斜率效率和输出光功率分别为1.1 W/A和38.2 W。测试得到外延材料的内损耗系数和内量子效率分别为0.58 cm~(-1)和91.6%。测试分析表明,器件电光效率的提高主要在于新型的InGaAs/GaAsP应变补偿量子阱和大光腔结构设计。

CMOS超高频整流器

提出了一个适用于无源UHF RFID标签芯片的全CMOS整流器.整流器包括射频-直流转换电路、偏置电路、直流-直流转换电路和振荡器电路.整流器的工作频率范围是860～960 MHz.基于0.18μm,1p6m的标准数字CMOS工艺,设计并实现了无源UHF RFID标签芯片的整流器.该设计采用开关电容电路技术动态地消除了CMOS管开启电压的问题,在标准数字CMOS工艺下实现了高效率的超高频整流器.整流器的面积为180μm×140μm.当输入900MHz,-16dBm的射频信号时,整流器的输出电压为1.2V,启动时间为980μs.

980nm单模运转未镀增透膜光纤光栅激光器

提出了一种工艺简单的980 nm未镀增透膜的光纤光棚外腔半导体激光器.首先从理论上分析了边模抑制比(SMSR)与激光二极管前表面反射率R2、外腔长Lext和激光二极管-光纤耦合效率之间的关系,得出边模抑制比随R2和Lext的增大而减小,而随着激光二极管-光纤的耦合效率的提高而增大.从计算结果中还可以看出,即使半导体激光器不镀增透膜(R2=0.3时),在其它参量合适的情况下,边模抑制比仍可大于40 dB.然后,对其进行实验验证,在半导体激光器未镀模的情况下,选择光纤光栅发射率为0.5,外腔长为12.5 cm,输入电流为28.8 mA(约为阈值电流的2.4倍)时,通过仔细调节恒温、恒流电路,实现了边模抑制比高于40 dB的稳定的单纵模输出,外腔激光器的线宽优于1.6 MHz.