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.

Investigation on integrated high speed DFB light source and narrow bandwidth RCE photodetector for WDM fiber communication network application

Electroabsorption (EA) modulator integrated with partially gain coupling distributed feedback (DFB) lasers have been fabricated and shown high single mode yield and wavelength stability. The small signal bandwidth is about 7.5 GHz. Strained Si1-chiGechi/Si multiple quantum well (MQW) resonant-cavity enhanced (RCE) photodetectors with SiO2/Si distributed Bragg reflector (DBR) as the mirrors have been fabricated and shown a clear narrow bandwidth response. The external quantum efficiency at 1.3 mum is measured to be about 3.5% under reverse bias of 16 V. A novel GaInNAs/GaAs MQW RCE p-i-n photodetector with high reflectance GaAs/ALAs DBR mirrors has also been demonstrated and shown the selectively detecting function with the FWHM of peak response of 12 nm.

Modal correction for fiber-coupling efficiency in free-space optical communication systems through atmospheric turbulence

High-speed free-space optical communication systems have recently used fiber-optical components. The coupling efficiency with which the received laser beam can be coupled into a single-mode fiber is noticeably limited by atmospheric turbulence due to the degradation of its spatial coherence. Fortunately, adaptive optics (AO) can alleviate this limitation by partially correcting the turbulence-distorted wavefront. The coupling efficiency improvement provided by Zernike modal AO correction is numerically evaluated. It is found that the first 3-20 corrected polynomials can considerably improve the fiber-coupling efficiency. The improvement brought by AO is compared with that brought by a coherent fiber array. Finally, a hybrid technique that integrates AO and a coherent fiber array is proposed. Results show that the hybrid technique outperforms each of the two above-mentioned techniques. (C) 2009 Elsevier GmbH. All rights reserved.

Direct electron communication between glucose oxidase and carbon electrode covered with polypyrrole

Glucose oxidase can be effectively adsorbed onto the polypyrrole(PPy) thin film electrochemically formed on an anodized galssy carbon electrode(GCEa). Direct electron communication between the redox of GOD and the modified electrode was successfully achieved, which was detected using cyclic voltammetry. GOD entrapped in PPy film still remained its biological activity and could catalyze the oxidation of glucose. As a third generation biosensor, GOD-PPy/GCEa responded linearly up to 20 mM glucose with a wider linear concentration range.

H5N1 avian influenza re-emergence of Lake Communication Qinghai: phylogenetic and antigenic analyses of the newly isolated viruses and roles of migratory birds in virus circulation

Highly pathogenic avian influenza H5N1 virus has swept west across the globe and caused serious debates on the roles of migratory birds in virus circulation since the first large-scale outbreak in migratory birds of Lake Qinghai, 2005. In May 2006, another outbreak struck Lake Qinghai and six novel strains were isolated. To elucidate these QH06 viruses, the six isolates were subjected to whole-genome sequencing. Phylogenetic analyses show that QH06 viruses are derived from the lineages of Lake Qinghai, 2005. Five of the six novel isolates are adjacent to the strain A/Cygnus olor/Croatia/1/05, and the last one is related to the strain A/duck/Novosibirsk/ 02/05, an isolate of the flyway. Antigenic analyses suggest that QH06 and QH05 viruses are similar to each other. These findings implicate that QH06 viruses of Lake Qinghai may travel back via migratory birds, though not ruling out the possibility of local circulation of viruses of Lake Qinghai.

植入式广告与普通插播广告的效果比较及其影响因素

Brand placement is to present the information of products and brands through certain entertainments and non-commercial areas. Since 1990's, brand placement has become a major way of spreading advertisement and a new growing point of the global advertising market. In china, it is easily seen from spring festival evening gala of CCTV to all kinds of movie and TV shows, and is thus interested by many brand owners, advertisers and communication researchers. Since 2006, the people in the media circles have begin to take full care of the study of the brand placement. In general, there is still certain distance between the theoretical studies and the reality. It's a general problem over the world and is especially true for China as this was just a new idea. As the biggest global economic entity, China is the most potential and powerful market, thus the market of the brand placement will be huge. To push its development, it's then crucial to have theoretical studies on it. Many questions have not been explained yet in this area, mostly essential is to ask what kind of advantage it acquires compared with the traditional advertisement, if there is, how does such advantage show? What kind of factors influents the market effect of the brand placement? All these questions are not answered yet. Also it's well-known that a successful advertisement relies heavily on the understanding of the culture. Thus a specific thing to deal with is to study the effects according to the Chinese culture, which can make constructive suggestion to the whole industry. Our research is to compare the effects between the brand placement with the ordinary media advertisements, discuss its possible influences, and try to make certain suggestions to the future running and development. Our research obtains the following results by using the movie and advertisement in reality: (1) Like ordinary media ad’s, brand placement can improve the brand recognition of the audience significantly. (2) The ordinary ad's make the people easier to remember them than brand placement, while not too much difference in the brand recognition. (3) The brand placement has a significant 'emotional shifting' effect, i.e. the more positive to the movie, the more you love the built-in brand. (4) It is an important factor that how much brand information is involved in the movie; while how much the plot is involved has great impact on the 'emotional shifting' effect. (5) The familiarity is a great factor for the ad's, it's obvious that the popular products get way better effects through brand replacement. (6) An effective way is to choose those positive, interesting and eye-catching movies and TV shows as carriers of the brand and to use it as natural as possible.