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Novel tunable laser sources with 1.5-μm and 1.57-μm cascaded DFB reflectors for in situ gas monitoring applications

Sensors and Actuators, B: Chemical 2009年第2期140卷 371-377页

作者： Yao, Chiu-Lin Lee, San-Liang Hung, Yung-Jr Pan, Yen-Ting Jeng, Jing-Lyang Wang, Hsiu-Che Department of Electronic Engineering National Taiwan University of Science and Technology 43 Keelung Rd. Sec. 4 Taipei 106 Taiwan Energy and Resources Laboratories Industrial Technology Research Institute Taiwan

Novel tunable lasers based on 1.5-μm and 1.57-μm cascaded distributed-feedback reflectors are realized for real-time monitoring of H2O and CO gas mixtures immediately in multi-gas sensor systems. With simple fabrication procedures, the new design allows the realization of a widely tunable laser source that can cover the H2O and CO absorption wavelength bands. With the temperature tuning of 0.1 nm/°C and current tuning of 0.014 nm/mA, the laser can be tuned to cover over 3 nm wavelength range in each wavelength band. Experiments verify that the lasers can have more than 38 dB SMSR over the tuning range. The characteristics of high power, excellent spectral purity, and simple wavelength switching control can simplify the analysis procedures of gas sensing and thus reduce the cost. By direct absorption method, the tunable laser has been successfully adopted in a diode laser sensor system for monitoring of water vapor concentration near 1.5 μm and carbon monoxide near 1.57 μm. Less than 15% error in the line strength is observed between the measured data and HITRAN database. © 2009 Elsevier B.v. All rights reserved.

关键词： Light absorption

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Fabrication and process characterization of atom transistor chips

Fabrication and process characterization of atom transistor ...

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International conference on Solid State Sensors and Actuators (TRANSDUCERS)

作者： H.C. Chuang E.A. Salim v. vuletic D.Z. Anderson v.M. Bright Department of Mechanical Engineering University of Colorado Boulder CO USA Department of Mechanical Engineering National Taipei University of Technology Taipei Taiwan Department of Physics University of Colorado Boulder CO USA Harvard Center of Ultracold Atoms Massachusetts Institute of Technology Cambridge MA USA

This paper describes the design and fabrication of an atom chip for atom tunneling experiments. A fabrication process was developed that uses a combination of Uv-optical and Electron-Beam lithography to pattern micrometer and nanometer scale copper wires on a single chip. The minimum wire width fabricated in this work is 200 nm. The wires can carry current densities of more than 7.5times10 7 A/cm 2 . The electrical current tests establish the feasibility of realizing chip-based atom tunneling experiments.

关键词： Fabrication Tunneling Wires Potential well Physics Lithography Atomic measurements Mechanical engineering Nanowires Micromachining

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A novel magneto-optic switch based on nanosecond pulse

A novel magneto-optic switch based on nanosecond pulse

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Asia Communications and Photonics conference and Exhibition (ACP)

作者： Qingping Wu Jianjian Ruan Zihua Weng Shaohan Lin Changzhou College of Information Technology Changzhou China School of Physics and Mechanical & Electrical Engineering Xiamen University Xiamen China

With the rapid development of all-optical network, we bring forward more and more requirements to the performance of the optical switches. Therefore, a novel magneto-optic switch based on nanosecond pulse is designed and investigated in this study. It is characterized by no moving parts, high switching speed, and small size etc. The research of magneto-optic switch mainly involves the design of optical route and nanosecond pulse generator. The optical route designment includes the selection of magneto-optic crystal, the route designment and performance analysis of polarized light in the MO switches, as well as the design of magnetic route in Faraday rotator. A bismuth-substituted rare-earth iron garnet single crystal is chosen as magneto-optic material, and a current solenoid is used to generate the applied magnetic field. The design of nanosecond pulse generator is based on the avalanche multiplier effect of avalanche transistor. Many kinds of avalanche transistor are studied in the experiment. The experimental results indicate that the rise time of the output pulse is about 2–5ns, the pulse width is about 6–20ns, while the pulse amplitude is about 30–150v, thereby it is satisfying for the magneto-optic switch used in all-optic network. By controlling the magnetization of the magneto-optic material, the optical beam can be stably switched and the measured switching time is about 100–200ns.

关键词： Magnetic switching Magnetooptic effects optical switches optical pulses optical design Magnetic materials Space vector pulse width modulation Pulse generation optical materials All-optical networks

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Organic sensors for explosive detection

Organic sensors for explosive detection

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International conference on Computers and Devices for Communication (CODEC)

作者： Ravishankar S. Dudhe Seena v. Soumyo Mukherji Anil Kumar Ramgopal Rao Department of Electrical Engineering Indian Institute of Technology Bombay Mumbai INDIA School of Bio-sciences & Engineering Indian Institute of Technology Bombay Mumbai INDIA Department of Chemistry Indian Institute of Technology Bombay Mumbai INDIA

Organic field effect transistors and polymer microcantilevers are two different classes of organic sensors with potential applications in biochemical sensing. Organic field effect transistors based on poly (3-hexylthiophene) and CuII tetraphenylporphyrin composite were investigated as sensors for detection of vapors of nitrobased explosive compounds. Significant changes, suitable for sensor response, were observed in transistor -on|| current (Ion) and conductance (S) after exposure. A similar device response was, however, not observed for oxidizing agents such as benzoquinone and benzophenone. Polymer microcantilevers offer a sensitive cost effective platform for explosive gas detection. These sensors with optical and electrical transduction mechanisms were designed and fabricated using SU-8 polymer and they are further functionalized with appropriate coating for explosive detection. optical and electrical responses of respective microcantilevers to TNT vapors are also reported here.

关键词： Explosives Biosensors optical sensors optical polymers OFETs Biomedical optical imaging Costs Particle beam optics optical design Polymer films

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Glottal space segmentation from motion estimation and gabor filtering

Glottal space segmentation from motion estimation and gabor ...

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Annual International conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： A. Mendez E.M. Ismaili Alaoui B. Garcia E. Ibn-Elhaj I. Ruiz University of Deusto Bilbao Spain Faculty of Sciences University Mohammed V Agdal Rabat Rabat Morocco National Institute of Posts and Telecommunications (INPT) Rabat Morocco

Obtaining the glottal space segmentation is essential to characterize morphological disorders of vocal folds. In this study, the tested images are been acquired by direct optical inspection of the glottis using an endoscope and most of them are very poor quality. The application of motion estimation is very useful to segment the vocal folds endoscopic videos without user interaction. This approach involves three process steps: 1) Wiener motion estimator - to shift the measurement the next frame regarding to the current frame, and look for similarities between them. The best matching will accurate a shift equal to the displacement vector of the object; 2) Segmentation using motion estimation results and applying Gabor filtering; 3) Experimental results to demonstrate that the proposed method is effective. Our proposal works correctly with 95% of database test videos and it shows a great advance in design, and in the nearby future, a complete method to diagnose vocal folds pathologies.

关键词： Motion estimation Gabor filters Image segmentation optical filters Filtering Testing videos Inspection Endoscopes current measurement

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Spectroscopic simulation of tapered laser diodes

Spectroscopic simulation of tapered laser diodes

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High Power Diode Lasers and Systems conference (HPD)

作者： J.J. Lim E.C. Larkins P. Bream N. Michel M. Krakowski S. Sujecki Photonic and RF Engineering Group Electrical Systems and Optics Research Division Engineering University of Nottingham Nottingham UK Alcatel Thales III-V Laboratory Palaiseau France

In this work, the authors have presented a description of our spectral laser model and performed spectroscopic simulations of a 975 nm tapered laser diode. To verify the ASE model, we checked the extracted gain using the variable stripe length method. A good agreement between the simulated and measured emission linewidth could be obtained using a spontaneous emission coupling factor of 1×10 -16 . The simulated redshift in the peak emission wavelength with increasing bias is consistent with experiment and is attributed to self-heating effects.

关键词： Spectroscopy Diode lasers Laser modes Spontaneous emission Stimulated emission optical pumping Equations current density design engineering Laser excitation

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Terahertz CMOS circuit design and applications for ultra-high data rate (>100Gbps) communication

Terahertz CMOS circuit design and applications for ultra-hig...

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2009 8th IEEE International conference on ASIC, ASICON 2009

作者： Chang, Mau-Chung Frank UCLA United States US National Academy of Engineering United States

ISBN: (纸本)9781424438686

Wedged between traditional microwave and optics, the term "Terahertz" was first named by Fleming to designate EM spectrum range from 300GHz to 3THz. It remains one of the least tapped spectra over time. Terahertz image and spectroscopic systems have drawn substantial attention recently due to their unique capabilities in detecting and/or analyzing concealed objects through fog and fabrics. The generation of practical Terahertz signals is nevertheless nontrivial and can only be accomplished by using Free-Electron Radiation, optical Lasers, Gunn Diodes and sometimes oscillators made of III-v compound based HBT/HEMTs. However, these prior arts suffer major disadvantages of size, cost, complexity, efficiency and/or even cryogenic cooling to produce meaningful signals in the notorious "Terahertz Gap". In the past, commercial CMOS technology has never been seriously considered for ultra-high frequency (>100GHz) circuit/system applications due to its limited IT (current gain cut-off frequency) and fmax (maximum frequency of oscillation). However, continuous device scaling may shift the paradigm and enable further scaled CMOS to reach Terahertz in cut-off frequencies. According to 2007 ITRS, both IT and fmax of 32nm CMOS will approach the lower bound of the Terahertz (600-800GHz, respectively). Under such circumstances, can CMOS possibly play significant roles in the coming Terahertz era, especially for needed portable systems? This question may be answered by assessing some recent circuit innovations devised for Terahertz signal generation and detection. Among mm-Wave signal generation techniques, differential push-push oscillator has been widely adopted. To attain sufficient gain for circuit oscillation, designers often select fundamental oscillation frequency f0 near fmax/2. This, however, renders the achievable oscillation frequency equivalent or lower than that of fmax. In order to alleviate such limitation, we have recently developed a Linear Superposition (LS) techni

关键词： Millimeter waves

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A Control System design for the Optimal Bias Point of External Modulator

A Control System Design for the Optimal Bias Point of Extern...

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2009 9th International conference on Electronic Measurement & Instruments（ICEMI’2009）

作者： Yinan Chen Xiaoqing Zhang Dong Li School of Optoelectronic Information & Telecommunication engineering,Beijing Information Science & Technology University,Beijing,100192,China

This paper deals with the effects of direct current bias voltage to X-cut y conduction Mach-Zehnder intensity modulator’s export optical power,and achieves a cosine function equation of direct current bias voltage versus export optical power of *** modulator works on an approximate linear region nearby the optimal bias point v /2( r 10mv).Considering the approximate linear region’s range of variation is infinitesimal,a high-accuracy digital signal processing (DSP) control system has been designed which achieves precise control for the optimal bias point,in addition,its control precision can be attained 1mv.

关键词： external modulation,direct current bias voltage,light power,optimal bias point,automatic control

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Surface plasmon enhancement of optical absorption of thin film a-Si:H solar cells

Surface plasmon enhancement of optical absorption of thin fi...

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2009 34th IEEE Photovoltaic Specialists conference (PvSC)

作者： R. Biswas D. Zhou B. Curtin N. Chakravarty v. Dalal Department of Physics & Astronomy Ames Laboratory Iowa State University Ames IA USA Microelectronics Research Center Department of Electrical and Computer Engineering Iowa State University Ames IA USA

We design and fabricate a-Si:H solar cells with plasmonic crystal back reflectors demonstrating enhanced absorption of near infrared photons. Rigorous simulations predict plasmonic nanoparticles on ITO can increase absorption in the near infrared. Rigorous simulations also predict plasmonic crystal back reflectors with a pitch of ~750 nm to optimize the enhanced absorption. Such periodic back reflectors have been fabricated with photolithography and a-Si:H solar cells have been grown on them by PECvD. The solar cells display ~9% improvement in short circuit current and external quantum efficiency and a absorption enhancement factor exceeding 8 above 650 nm.

关键词： optical films Plasmons Photovoltaic cells Electromagnetic wave absorption Photonic crystals Predictive models Nanoparticles Indium tin oxide Circuit simulation Lithography

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The design of Wide BW frequency synthesizer based on the DDS&PLL hybrid method

The Design of Wide BW frequency synthesizer based on the DDS...

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2009 9th International conference on Electronic Measurement & Instruments（ICEMI’2009）

作者： Li YongKe Department of optical and Electronic engineering,Ordnance engineering College Shijiazhuang 050003,China

Frequency synthesizer is an important component in the modem electronic *** paper studied a kind of frequency synthesizer in the UAv system and put forward an improvement method for DDS (Direct Digital Synthesis) &PLL (Phase Locked Loop) hybrid frequency *** further to raise PLL performance in fast locking and noise immunity ability in the improvement method,a PLL with Analog Adaptive Bandwidth Control (AABC) has been designed in this *** new-type AABC has been presented based on conventional Charge pump PLL *** PLL with AABC block can control the loop bandwidth according to the locking status and the amount of inputs' phase error adaptively;and consequently low-noise and fast-lock performance are ***,the designed Frequency synthesizer satisfies an 800MHz to 1.8GHz output range and a 0.4ms maximum conversion *** at 900MHz,the phase noises are-93dBc/Hz at 200 kHz offset,and the whole circuit draws 8.7mA current from 3.0v supply.

关键词： Frequency synthesis,PLL,DDS,phase-noise,spurious

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