Tolerance analysis for incident angle of volume phase holographic grating used in optical channel performance monitor

Transmission Volume Phase Holographic Grating (VPHG) is adopted as spectral element in the real-time Optical Channel Performance Monitor (OCPM), which is in dire need in the Dense Wavelength -division-multiplexing(DATDM) system. And the tolerance of incident angle, which can be fully determined by two angles: 6 and (p, is finally inferred in this paper. Commonly, the default setting is that the incident plane is perpendicular to the fringes when the incident angle is mentioned. Now the situation out of the vertical is discussed. By combining the theoretic analysis of VPHG with its use in OCPM and changing 6 and (0 precisely in the computation and experiment, the two physical quantities which can fully specify the performance of VPHG the diffraction efficiency and the resolution, are analyzed. The results show that the diffraction efficiency varies greatly with the change of 6 or (p. But from the view of the whole C-band, only the peak diffraction efficiency drifts to another wavelength. As for the resolution, it deteriorates more rapidly than diffraction efficiency with the change of (p, while more slowly with the change of theta. Only if \phi\less than or equal to+/-1degrees and alpha(B) -0.5 less than or equal to theta less than or equal to alpha(B) + 0.5, the performance of the VPHG would be good enough to be used in OCPM system.

Long-wavelength Si-based MQW photodetectors for application in optical fiber communication

Si-based SiGe/Si strained MQW long-wavelength photodetectors (PD) with cycle type (Ring Shape) waveguide (CWG) and resonant-cavity-enhanced (RCE) structure have been investigated for the first time for improving the quantum efficiency and response time. The results show that the responsivities are higher than that of conventional PD with a same Ge content reported previously. In addition, RCE-PD has an obvious narrow band response with FWHM less than 6nm.

Wavelength tunable electroabsorption modulated DFB baser with thin film heater

　

Long-wavelength SiGe/Si MQW resonant-cavity-enhanced photodiodes (RCE-PD)

Si1-xGex/Si optoelectronic devices are promising for the monolithic integration with silicon-based microelectronics. SiGe/Si MQW RCE-PD (Resonant-Cavity-Enhanced photodiodes) with different structures were investigated in this work. Design and fabrication of top- and bottom-incident RCE-PD, such as growth of SiGe MQW (Multiple Quantum Wells) on Si and SOI (Si on insulator) wafers, bonding between SiGe epitaxial wafer and SOR (Surface Optical Reflector) consisting Of SiO2/Si DBR (Distributed Bragg Reflector) films on Si, and performances of RCE-PD, were presented. The responsivity of 44mA/W at 1.314 mum and the FWHM of 6nm were obtained at bias of 10V. The highest external quantum efficiency measured in the investigation is 4.2%.

Modification of emission wavelength of self-assembled In(Ga)As/GaAs quantum dots covered by InxGa1-xAs(0 <= x <= 0.3) layer

Red shifts of emission wavelength of self-organized In(Cla)As/GaAs quantum dots (QDs) covered by 3 nm thick InxGa1-xAs layer with three different In mole fractions (x = 0.1, 0.2 and 0.3, respectively) have been observed. Transmission electron microscopy images demonstrate that the stress along growth direction in the InAs dots was reduced due to introducing the InxGa1-xAs (x = 0.1, 0.2 and 0.3) covering layer instead of GaAs layer. Atomic force microscopy pictures show a smoother surface of InAs islands covered by an In0.2Ga0.8As layer. It is explained by the calculations that the redshifts of the photoluminescence (PL) spectra from the QDs covered by the InxGa1-xAs (x greater than or equal to 0.1) layers were mainly due to the reducing of the strain other than the InAs/GaAs intermixing in the InAs QDs. The temperature dependent PL spectra further confirm that the InGaAs covering layer can effectively suppress the temperature sensitivity of PL emissions. 1.3 mum emission wavelength with a very narrow linewidth of 19.2 mcV at room temperature has been obtained successfully from In,In0.5Ga0.5As/GaAs self-assembled QDs covered by a 3-nm In0.2Ga0.2As strain reducing layer. (C) 2001 Elsevier Science B.V. All rights reserved.

THEORETICAL AND EXPERIMENTAL STUDY OF POLARIZATION CHARACTERISTICS OF POLARIZATION MAINTAINING FIBER BASED ON WAVELENGTH-SWEEPING MODULATION

We analyze theoretically the polarization characteristics of polarization maintaining fiber and study the basic measurement principles of beat length and polarization extinction ratio of this kind of optical fiber. According, to the dependence of the phase difference between two orthogonally polarized modes (denoted Os HE(11)(x) and HE(11)(y)) transmitted in the polarization maintaining fiber on the light wavelength, we propose the wavelength-sweeping modulation method to measure the beat length and the model birefringence. Based on this technique, the hew length and polarization extinction ratio of the PANDA polarization maintaining fibers (PMFs) (provided by Yangtze Optical Fiber and Cable Company, Wuhan, China) were investigated in detail. Experimental results show good consistent with the theoretical ones. We find that this method shows high measurement precision with the advantages of clear measurement principle and easy to operate. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1466-1469, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25244

Generation of optimized wavelength-tunable optical pulse from an uncooled gain-switched Fabry-Perot semiconductor laser using optical amplifier as external light injection

We present a novel system design that can generate the optimized wavelength-tunable optical pulse streams from an uncooled gain-switched Fabry-Perot semiconductor laser using an optical amplifier as external light source. The timing jitter of gain-switched laser has been reduced from about 3 ps to 600 fs and the pulse width has been optimized by using our system. The stability of the system was also experimentally investigated. Our results show that an uncooled gain-switched FP laser system can feasibly produce the stable optical pulse trains with pulse width of 18 ps at the repetition frequency of 5 GHz during 7 h continuous working. We respectively proved the system feasibility under 1 GHz, 2.5 GHz and 5 GHz operation. (c) 2008 Elsevier B.V. All rights reserved.

Influence of Laser Wavelength on Laser-induced Breakdown Spectroscopy Applied to Semi-Quantitative Analysis of Trace-Elements in a Plant Sample

Laser-induced breakdown spectroscopy (LIBS) as a powerful analytical technique is applied to analyze trace-elements in fresh plant samples. We investigate the LIBS spectra of fresh holly leaves and observe more than 430 lines emitted from 25 elements and molecules in the region 230-438 nm. The influence of laser wavelength on LIBS applied to semi-quantitative analysis of trace-element contents in plant samples is studied. The results show that the UV laser has lower relative standard deviations and better repeatability for semi-quantitative analysis of trace-element contents in plant samples. This work may be helpful for improving the quantitative analysis power of LIBS applied to plant samples.

高性能硅基锗光电探测器的研制

在信息产业、生物医学等科技领域越来越受关注的今天，新型光电子、光通信科技必将以更快的速度发展。Si基光电子集成采用成熟价廉的微电子加工工艺，将光学器件与多种功能的微电子电路集成，是实现光通信普及发展和光互连的有效途径。Si基光电探测器是Si基光通信系统的关键器件之一。随着近年来Si基Ge材料外延技术的突破性进展，Si基Ge光电探测器因为兼顾了Si基光电子集成和对光通讯波段(1.31和1.55μm)的高效探测，成为了当今研究的一大热点。
    半导体光电探测器的性能与其结构密切相关。PIN型光电探测器是最常见的探测器，可以普遍应用于光通讯光互连系统；雪崩光电二极管(APD)因为具有较高的响应度和内部增益，在实现单光子探测方面具备很大的优越性，适用于当今迅猛发展的生物光子学和量子信息学；共振腔增强型的光电探测器(RCE-PD)，集波长选择器、高速光信号接收器于一体，而且具备共振增强作用、高饱和功率输出等特点，是局域网、光纤入户和现代波分复用(Wavelength-Division Multiplexing,WDM)系统光通信网络的一种优选方案；波导结构探测器(Waveguide-PD)可以解除探测器的响应带宽和量子效率之间的矛盾，而且其结构特点更易于实现与调制器等光波导器件的集成，是片上光互连的首选探测器。
    本论文围绕高性能Si基Ge光电探测器这一研究目标，开展了多种结构的光电探测器的研制，包括PIN型PD的研制及其优化、吸收区与倍增区分离结构(SACM)的Ge-on-Si APD、RCE-PD和Waveguide-PD，主要研究结果如下：

1.                成功研制了PIN型Ge-on-Si光电探测器，器件在-1V外加偏压下暗电流密度为46.6mA/cm2，在1.31μm和1.55μm波长下器件的量子效率分别为40%和17%；然后改进了实验方法，在制作器件之前将Ge-on-Si材料在850℃条件下快速退火1分钟，从而改善材料质量，器件的暗电流密度降低至4mA/cm2，这是目前国际上报道的最好结果之一。

2.                研制出了PIN型Ge-on-SOI光电探测器，在1.31μm和1.55μm波长的量子效率分别为62%和25%。在-3V外加偏压下，器件的3dB带宽为12.6GHz。25μm直径器件，3dB带宽更是达到了13.4GHz。同时，制作了均匀性很好的1×4探测器阵列，单个器件的3dB带宽达13.3GHz。

3.                在国际上首次研究了硅基锗光电探测器的高饱和特性。在-1V和-2V外加偏压下，探测器的1-dB小信号压缩电流分别为22mA和40mA,相应的光功率分别为67.5mW和110.5mW。

4.                成功研制了吸收区和倍增区分离的Si基Ge雪崩光电二极管，器件的穿通电压Vpt约为29V，击穿电压Vbd(暗电流等于100μA时的电压)为39.5V。在击穿电压附近，如39V时，SACM-Ge-on-Si APD的增益为40。

5.                解决了背面ICP深刻蚀工艺难题，成功制备了中心波长在1.55μm，量子效应高达62%的共振腔增强型Si基Ge光电探测器。

Tunability of resonant wavelength by Fabry-Perot microcavity in organic light-emitting diodes

Distributed Bragg reflectors (DBR) with different reflection wavelengths were designed, and were used to fabricate microcavity organic light-emitting diodes (OLEDs) based on tris(8-hydroxyquinoline)-aluminum (Alq(3)) as the emitter and N, N'-di(naphthalene-1-yl)-N, N'-diphenyl-benzidine (NPB) as the hole-transporting layer. The microcavity was composed of DBR dielectric mirror and metal electrode aluminum (Al) mirror. Some effects of vertical optical Fabry-Perot microcavity on spontaneous emission in OLEDs were investigated. Spectral narrowing, enhancement of emitting intensity and anglular dependence of emission were observed due to the microcavity effect. It was found experimentally that the utilization of DBR is a better method to adjust the emissive mode in the resonant cavity in OLEDs well. Thus the realization of different color light emission becomes possible by the combination of carefully designed microcavity and electroluminescent organic semiconductors in a single LED.

Measurement of the single-color three-photon resonant ionization spectrum of atomic uranium under the "equivalent wavelength effect laser" interaction

Using Nd: YAG laser (532 nm) pumped mixed-dye laser. we obtained the output of this dye enhanced at the wavelength interval equivalent to that given by the copper vapor laser pumped dye laser. This measure favored is with the measurement of single-color three-photon resonant ionization spectrum of atomic uranium in the range of 562-586 nm,which is otherwise not efficiently covered by Nd: YAG laser pumped dye laser with any single dye. Thus 140 U I energy levels were obtained and the peaks of interest 575.814 nm and 575.836 rim were well resolved and their relative intensity determined.