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Abstract:We use Joness matrix method and the global optimal method to investigate the propagation characteristic of surface acoustic wave(SAW) for X-cut single crystal Lithium Niobate(LiNbO₃). As an application, a novel integrated acousto-optical filter, which allows to minimize the dimension of AO cells and suppress side-lobes, was designed on the base of LiNbO₃ crystal. Supported by the National Natural Science Foundation of China (No. 60478036)

Abstract:The general principles and realizations of FBG wavelength tuning with elastic beams are proposed and demonstrated. Theories and experiments show that when displacement at the center point of simple beams,deflection of cantilever beams and torsion strain of torsion beams are relatively small,Bragg wavelength shifts of sensing FBGs have linear relationship with applied external stress, lateral displacement,torque and torsional angles,respectively. The experimental results indicate that the curvature sensitivity of the simple beam is 1.65 nm/m^-1 ,the displacement sensitivity of the equivalentstrain cantilever beam is 4.4 cm/kg and the torque and torsional angle sensitivities of the torsion beam are 6.27 nm/Nm and 0.086 7 nm/degree,respectively.

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Abstract:We report on a high power output quasi-continuous-wave nanosecond optical parametric generator (OPG) of congruent periodically poled lithium niobate (PPLN) pumped by a 1064 nm acousto-opticallyQ-switched Nd: YVO₄ laser (duration: 70 ns, repetition rate: 45 kHz, spatial beam qualityM ²< 1.3). The OPG consists of a 38.7 mm long PPLN crystal with a domain period of 28.93 μ. With 5.43 W of average pump power the maximum average output power is 991 mW at 1517.1 nm signal wave of the PPLN OPG. Supported by the National Natural Science Foundation of China (Grant No 60278001 and No 10474071), the Science & Technology Cooperation Foundation of Nankai University and Tianjin University, the Ministry of Education, the Ph. D. Programs Foundation of Ministry of Education of China (Grant No 2020056001), Tianjin municipal technological development planning and the Outstanding Doctorate Dissertation of Tianjin University [2001]01.

Abstract:Fabrication of flexible organic light-emitting diodes (FOLEDs) with ITO/PVK: TPD/Alq₃/Al configuration prepared on PET substrates is reported. Alq₃ is used as the light-emitting material. The curves of the current density vs. voltage, optical current vs. voltage and quantum efficiency vs. current density of the devices are investigated. Compared the devices with the ones that have the same configuration and are fabricated under the same conditions but on glass substrates, the characteristics of the two kinds of devices are very similar except that the threshold voltage of the flexible FOLEDs is a little higher. Under the driving voltage of 20V, the corresponding brightness and the external quantum efficiency are 1000 cd/m² and 0.27%, respectively. In addition, the anti-bend ability of the devices is tested and the reasons of failure of the devices are analyzed. Supported by the National Natural Science Foundation (60276027), Tianjin Natural Science key Foundation (023800511), Tianjin Science Foundation (033601211), Tianjin Science Development Foundation for University (9903114), and the key subject of the material physics and the chemistry of Tianjin.

Abstract:Based on the semiconductor amplifiing properties and the structure of optical fiber wave guide an InP inner fiber is developed. The InP inner film fiber can be employed as a small size, broadband, and ultra-short fiber amplifier. The quantum size effects of the fiber are emphatically investigated in the work. Using the experimental data, we compare the effective mass approximation (EMA) with effective parameterization within the tight binding (EPTB) models for the accurate description of the quantum size effects in InP. The results show that the EPTB model provides an excellent description of band gap variation over a wide range of sizes. The Bohr diameter and the effective Rydberg energy of InP are calculated. Finally, the amplifiing properties of the InP inner film fiber are discussed due to the quantum size effects. This work is supported by the Nano-technology Special Project of Shanghai. (Grant No. 0352nm019) and National Natural Science Foundation Of China (Grant No. 60477032)

Abstract:With in situ optical emission spectroscopy (OES) diagnosis on VHF-generated H₂+SiH₄ plasmas, and with the measurements of deposition rate and structure of μc-Si: H thin films fabricated with VHF-PECVD technique at different substracte temperature, influence of substrate temperature on the deposition of μc-Si: H thin film and on its structural properties have been investigated. The results show that with the increase of substrate temperature, the crystalline volume fraction Xc and average grain size d are enhanced monotonously, but the deposition rate increases firstly and then decreases. The optimized substrate temperature for (μc-Si: H thin films deposition under our current growth system is about 210 °C, at which deposition rate 0.8 nm/s of μc-Si: H thin film with Xc?60% and d?9 nm can be obtained.

Abstract:In this paper, a new type of photonic crystal fiber with high birefringence is proposed and analyzed with a full-vector model based on the super-lattice and the plane-wave expansion model. Due to the two different sizes of the holes introduced into the cladding of the PCF, the fiber is two-fold rotational symmetry and appears to be with high birefringence. Numerical results demonstrate that a modal birefringence at wavelength 1.31 μm is 1.8×10⁻³ in the PCF with Λ=2.55 μm,d ₁/Λ=0.3 andd ₂/Λ=0.833. A near 200 nm SPSM region within the wavelength range from 1.4 μm to 1.6 μm is obtained. This work was supported by the National High Technology Research Program of China (No. 2004AA31g200).

Abstract:A novel full color SOP (system on panel) AMOLED display based on the MIUC polycrystalline silicon TFT technique, and a new control circuit for the panel, which can deal with both VGA and DVI input signals have been developed. To realize gray-scale a sub-frame technique has been designed and implemented by FPGA device, in which an I²C module has been inserted. Through actual circuit, the whole design has been proven and the advantages of the SOP AMOLED display panel have been confirmed. Supported by National 863 Project (No. 2004AA33570) and Key Project of National Natural Science Foundation of China (No. 60437030).

Abstract:A design of diode-pumped Nd: YAG laser with a single crystal that generates simultaneous laser action at the wavelengths of 1064 nm and 1319 nm was presented and continuous-wave (CW) of 588.9 nm was obtained for the first time by use of type-I critical phase-matching LBO crystal intracavity sumfrequency mixing. The maximum output power of 62 mW is achieved with an incident pump power of 1.8 W. The optical-to-optical conversion efficiency is up to 3.4%, and the power instability in 24 h is better than ±2.7%. Supported by Hi-Tech 863 project of People’s Republic of China (No. 2002AA311141)

Abstract:A theoretical model is developed for the laser-diode-pumped Tm³⁺-doped fiber amplifier, and a set of ordinary differential equations (ODEs) governing the dynamics of dual-wavelength pumping scheme (1.4μ+1.56μ) based on the rate equations and propagation equations was established. The relationship between the spectra gain and pump power was described and analyzed by numerically solving the ODEs. Spectral gain as a function of longitudinal position along the fiber was given to optimize the fiber length; spectral gain per unit length, and fractional inversion were used to explain the gain shift property of TDFA. The theoretical results agree well with the experimental data. Received 28 March Supported by China Scholarship Council, Natural Science Foundation of Shandong Province of China (grant no. Y2003G01 and Y2002G06), Research Fund for the Doctoral Program of Higher Education of China (grant no. 2002022048

Abstract:A novel kind of multi-quantum well infrared photodetector (QWIP) is presented. In the new structure device, a p-type contact layer has been grown on the top of the conventional structure of QWIP, then a small tunneling current is instead of the large compensatory current, which made the device low dark current and low noise characteristics. The measured result of dark current is consistent with the calculated result, and the noise of the new structure QWIP is decreased to one third of the conventional QWIP. Supported by National “973” program (TG2000068302)

Abstract:The temperature characteristics for the different lasing modes at 300 K of intracavity contacted InGaAs/GaAs Vertical Cavity Surface Emitting Lasers (VCSELs) have been investigated experimentally by using the SV-32 cryostat and LD2002C5 test system. In combination with the simulation results of the reflective spectrum and the gain peak at different temperatures, the measurement results have been analyzed. In addition, the dependence of device size on temperature characteristics is discussed. The experimental data can be used to optimally design of VCSEL at high or cryogenic temperature. Supported by National Natural Science Foundation of China (No. 60276033), National High Technology Research and Development Program of China (No. 2002AA312070), National Key Basic Research Plan of China (No. G20000683-02), and Beijing Natural Science Foundation of China (No. 4021001).

Abstract:A diode-pumped Nd: YAG acousto-optically (A-O)Q-switched laser at wavelength 946 nm formed with a simple plane-plane cavity has been demonstrated. The maximum average output power was 850 mW. The highest peak power was 531 W with the pulse repetition rate of 20 kHz and pulse width of 80 ns at the incident pump power of 19.5 W. Supported by Key National Science Foundation of Shandong Province(Z2003A01)

Abstract:A novel method to measure the gain and refractive index characteristics of traveling-wave semiconductor optical amplifier (TMA) is presented. In-out fiber ends of TWA are used to construct an external cavity resonator to produce big ripple on amplified spontaneous emission (ASE) spectrum. By this means, Hakki-Paoll method is adopted to obtain the gain spectra of TWA over a wide spectral range. From measured longitudinal mode spacing and peak wavelength shift due to increased bias current, we further calculate the effective refractive index and the refractive index change. Special feature of refractive index change above lasing threshold is revealed and explained.

Abstract:The cascaded chirp fiber Bragg gratings (CFBGs) with ITU-T standard wavelengths and wavelength grid are applied to compensate the dispersion of 8×10 Gb/s WDM system. The ASE of the EDFA could be reduced, the OSNR of the transmitted signal can be increased and the fluctuation of the EDFA gain can be restrained in a certain scope by the CFBG employed in the system. Experiment of error-free 8×10 Gb/s 2015 km transmission without FEC and electric regeneration is demonstrated in this paper. In this system, only EDFA is used as amplifier, and no other form of dispersion compensator is adopted except CFBG. The experimental result showed that after 2015 km transmission, the consistency of the dispersion compensating for each channel is perfect. Supported by the National 863 Project (No. 2001AA122012) and the NSFC(No. 60337010)

Abstract:A novel drop unit for the optical code-division multiple access (OCDMA) based on fiber Bragg gratings and two-dimensional wavelength-time code is studied. The simple OCDMA drop unit can drop a code channel without disturbing the rest code channels. A similar unit for dropping a group of code channels is also proposed. Numerical simulation is given. The system delay can decrease by substituting the electrieal driving optical switch with a specific optical driving. The single channel drop unit can also be the basis for multiple channels drop. Supported by National Hi-tech 863 project (No. 2002 AA 311141)

Abstract:In the simulation of Intensity Modulation-Direct Detection WDM Systems, when the dispersion and nonlinear effects play equally important roles, the intensity fluctuation caused by cross-phase modulation may be overestimated as a result of the improper step size. Therefore, the step size in numerical simulation should be selected to suppress false XPM intensity modulation (keep it much less than signal power). According to this criterion, the step size is variable along the fiber. For a WDM system, the step size depends on the channel separation. Different type of transmission fiber has different step size. In the split-step Fourier method, this criterion can reduce simulation time, and when the step size is bigger than 100 meters, the simulation accuracy can also be improved. This work is supported by Nation Nature Science Foundation of China (50278001) and the Science & Technology Cooperation Foundation of Nankai University, the Ministry of Education.

Abstract:A new non-contact inspection technique based on laser-PSD (position sensitive detector) to inspect the inner surface of small-diameter pipe is proposed, and the corresponding sensor has been developed. After being reflected by two mirrors in series, a laser beam is projected onto the inner wall of a pipe as a small light spot and is read by a two-dimensional PSD. Based on the signals from the PSD and the structure parameters of the sensor, the spot position on the wall can be calculated in a local 3D coordinate system. The spot controlled by the micro-motor driven mirrors will scan a closed section ring on the inner wall of the pipe to obtain the relative coordinates of all the sampled points. The data will be then processed through data segmentation and least square fitting, to reconstruct the section curve used for obtaining the radius and the defect description of the section. Driven by a micro-pipe robot, the sensor can inspect a long curved pipe and obtain its 3-D reconstruction. An inspection system based on this technique can detect the mini-diameter pipe with an inner diameter of 9.5 mm≈10.5 mm and a curvature radius larger than 100 mm at a measurement accuracy of the inner surface defect of ±0.1 mm. This work Supported by the National High-Tech Program (No. 2001AA423130)

Abstract:A method for gazing-detection of human eyes using Support Vector Machine (SVM) based on statistic learning theory (SLT) is proposed. According to the criteria of structural risk minimization of SVM, the errors between sample-data and model-data are minimized and the upper bound of predicting error of the model is also reduced. As a result, the generalization ability of the model is much improved. The simulation results show that, when limited training samples are used, the correct recognition rate of the tested samples can be as high as 100%, which is much better than some previous results obtained by other methods. The higher processing speed enables the system to distinguish gazing or not-gazing in real-time. Supported by National Natural Science Foundation of China (No. 60478036)

Abstract:This paper introduces a robust global nonlinear optimizer—differential evolution (DE), which is a simple evolution algorithm to search for an optimal transformation that makes the best alignment of two sets of feature points. To map the problem of matching into the framework of DE, the objective function is proportional to the registration error which is measured by Hausdorff distance, while the parameters of transformation are encoded in floating-point as the functional variables. Three termination criteria are proposed for DE. A simulation of 2-dimensional point sets and a similarity transformation are presented to compare the robustness and convergence properties of DE with genetic algorthms (GA). And the registration of an object and its contour model have been demonstrated by using of DE to natural images.

Abstract:In this paper,spatially angular multiplexing technique in pulsed digital holography and an optical system based on this technique are introduced. Optical simulation and calculating analysis show that the designed system can be employed to record ultra-fast events of a time resolution in nanosecond.

Abstract:Monte Carlo simulation of the diffusing temporal light correlation in a multi-layered turbid medium is considered. A straightforward formula is introduced to calculate accurately and efficiently the autocorrelation function at any detector position. The simulation results are in an excellent agreement with an analytical solution of the correlation diffusion equation.

Abstract:In this paper, we calculate the resolution of a photorefractive incoherent-to-coherent optical converter on the image plane for small diffraction efficiency by taking into account the optical imaging characteristics of the imaging lens. For a thin grating,we obtain a high resolution,which is comparable with the experimental results.

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