Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:A novel 1.55 μ spot-size converter integrated with electroabsorption modulator is designed and fabricated with conventional photolithography and chemical process. For the modulator, we employed a deeply-etched ridge waveguide structure with polyimide on each side of its walls. For the spot-size converter, we employed a buried double-core structure in which a ridge-based passive wavegude is incorporated. The wide and thim passive waveguide is optically combined with a laterally tapered active waveguide to control the mode size. By simulation, the figure of merit is 4. 17 (dB/V/ 100 μ) and the beam divergence angles in teh horizontal and vertical directions are as small as 11. 2† x 13. 0† respectively. Supporred by the Natural Science Foundation of China (90101023) and national “973” Project (20000683-1)

Abstract:Hydrogen-like donor impurity states in symmetric triangular quantum wells are investigated by using a variational method. Both the effects of the variable effective mass of electrons and the spatially dependent dielectric constant are considered in the calculation. The numerical results show that the binding energy depends on not only the effective mass and dielectric constant but also the spatial distribution of electron probability density. The binding energies of donor states get the maximums at the wellcenter. The results are also compared with those obtained in parabolic and square wells. It is seen that the triangular well support the highest binding energies for donor states.

Abstract:The mode frequency and the quality factor of nanowire cavities are calculated for the intensity spectrum obtained by the finite-difference time-domain (FDTD) technique and the Padé approximation. In the free-standing nanowire cavity with the dielectric constant ε=6.0 and the length of 5 μ, the quality factors of 130, 159, and 151 are obtained for modes with frequency around 798 THz, at the cavity radius of 60 nm, 75 nm, and 90 nm, respectively. The obtained field distribution of the fundamental transverse mode shows that the mode field is confined very well by the nanowire cavity even when the radius of nanowire is much smaller than the mode wavelength.

Abstract:The nanocrystalline SiC films were prepared on Si (111) substrates by rf magnetron sputtering and then annealed at 800°C and 1000°C for 30 minutes in a vacuum annealing system. The crystal structure and crystallization of as-annealed SiC films were determined by the Fourier transform infrared (FTIR) absorption spectra and the X-ray diffraction (XRD) analysis. Measurement of photoluminescence (PL) of the nanocrystalline SiC (nc-SiC) films shows that the blue light with 473 nm and 477 nm wavelengths emitted at room temperature and that the PL peak shifts to shorter wavelength side and the PL intensity becomes stronger as the annealing temperature decreases. The time-resolved spectrum of the PL at 477 nm exhibits a bi-exponential decay process with lifetimes of 600 ps and 5 ns and a characteristic of the direct band gap. The strong blue light emission with short PL lifetimes suggests that the quantum confinement effect of the SiC nanocrystals resulted in the radiative recombination of the direct optical transitions. The project supported by the National Natural Science Foundation of China (Grant No. 60476003)

Abstract:Fiber Bragg grating under transverse force on a small grating section is studied by numerical simulation and experimentation. A numerical simulation based on the transfer matrix method is used to calculate the consequent changes in reflected spectrum. The reflected spectra of the FBG subjected to the transverse force split into two main peaks, and the split point shifted linearly and periodically versus the applied force. The split point is shifted in the bandwidth with the period of 11N, and the sensitivity of the split point wavelength shift versus the applied force is 0.05 nm/N in one period. The experimental results show good agreement with the simulation analysis.

Abstract:The effects of using overall affix and two-spot affix between the FBG and underlay on the characteristics of the pressure sensors are compared both experimentally and theoretically. It is found that overall affix can produce large nonlinear effect on the characteristics of output of the sensors. The nonlinear effect caused by the expanded spectral width mainly due to the stress birefringence and the stress grads etc. The experimental result shows that the spectral width caused by using overall affix is 0.28 nm and the linearity can have up to 1.89% of increasing by using two-spot affix. The method of twospot affix can improve response characteristics of the sensor which is benefit to achieve wavelength demodulation and to improve measurement precision.

Abstract:A novel opening loop structure of fiber Bragg grating is proposed. From the analysis of the strain distribution at the side of the opening loop we found that the structure can be used as a new setup to linearly tune the central wavelength of the fiber Bragg gating. The setup is an uniform fiber Bragg grating bonded to the side of a beam which can produce an uniform strain. The experimental results show that the wavelength range of linear tuning is about 5.0 nm,the sensitivity is about 3. ]8 nm/N and the linearity is up to 0. 9988.The largest tuning range of the setup is about 11. 0 nm while the linearity is 0. 9941 in the ranae of 0 and 11. 0 nm. ExPerimental results are in good agreement with our theoretical analysis.

Abstract:We have demonstrated a laser-diode pumped Nd: GdVO₄ extra-cavity frequency tripling ultraviolet laser with a LBO crystal in this paper. Under the acousto-optic (A-O) Q-switched operation, we have obtained 355 nm ultraviolet laser, with pulse width of 25 ns and pulse repetition rate of 20 kHz. By using a type I non-critical phase-matched LBO crystal, the SHG output power of 822 mW is achieved at the incident pump power of 16 W. The output power of 355nm UV laser is 260mW with a type II phase-matched LBO crystal, and the conversion efficiency (1 064 nm-355 nm) is 5.9 %. The power stability of 355 nm laser is 1.7% in 1 h. Supported by Natural Science Foundation of Shandong under No. Z003A01.

Abstract:A simply method to measure the thermal focal length of a LD end-pumped Nd.GdVO4 solid state laser with a stable resonator is presented. By scanning a slit across the field with expression of multi-mode Gaussian distribution behind the output mirror of lasers, the radius and the M^2 factor describing the quality of beam can be measured. The waists of the multi-mode field and the TEM00 mode can be deduced according to the law of multi-mode Gassian beam propagation. Based on the ABOD matrix theory of a stable resonator,the thermal focal length of the active medium can be easily obtained. The thermal focal length of a LD end-pumped Nd. GdVO~ laser has been measured and the experimental results agree with the theoretically analyzed values.

Abstract:Supercontinuum (SC) generation in a dispersion-shifted fiber (DSF) pumped by a 10 GHz regeneratively mode-locked fiber laser (RMLFL) is presented. Optimization of pump wavelength leads to a 20 dB bandwidth of 58. 73 nm, which covers the whole C band and part of L band. Using an angle-tuning thin film filter, multi-wavelength and pico-second pulse trains of low chirp could be chosen from the SC spectrum. Amplified spontaneous emission(ASE) induced degeneration of the achieved pulse trains is observed and discussed. Supperted by National Natural Science Foundation of China (No. 60477022)

Abstract:In this paper, silica-on-silicon erbium-doped phosphosilicate glass film material was fabricated for optical waveguides by sol-gel method. Samples were characterized and analyzed. It is demonstrated that we have got well-distributed, good translucent, alterable thickness of film and glass state erbiumdoped phosphosilicate films material for optical waveguides by sol-gel method.

Abstract:The experimental study on negative capacitance (NC) of various light-emitting diodes (LEDs) is presented. Experimental result shows that all LEDs display the NC phenomenon. The voltage modulated electroluminescence (VMEL) experiment confirms that the reason of negative capacitance is the strong recombination of the injected carriers in the active region of luminescence. The measures also verify that the dependence of NC on voltage and frequency in different LEDs is similar; NC phenomenon is more obvious with higher voltage or lower frequency.

Abstract:In order to explain the phenomenon of negative capacitance (NC) in light emitting diodes LEDs, we present a new model based on local strong recombination in active region and firstly deduce the analytic expression of NC from continuity equation. The theoretical result indicates that the NC effeci becomes stronger when the carrier recombination rate increases in a certain range, which is consistent with the experimental result. Accordingly, we confirm that the NC is caused by carrier recombination in active region instead of by other exterior factors. This work was supported by the National Nature Science Foundation (Grant No. DMR-60376027).

Abstract:A 32-channel 50 GHz spaced arrayed-waveguide grating(AWG) with our innovative configuration has been designed and fabricated. The performance of the device has been fully tested by using a system that consists of a tunable laser light source (TLS), an optical power meter and a polarization controller. The insertion loss (IS) of the device is 4.2–7.4 dB. The crosstalk is about −28 dB. TheIS uniformity is less than 3.3 dB. With our configuration, the performance of the device has been enhanced effectively and the difficulty in alignment process has been decreased obviously. Project supported by Nation Key Basic R&D Plan of China (G2000036602), and the National Natural Science Foundation of China (No. 69889701)

Abstract:In this paper,we present a new self-similar traffic shaping mechanism and investigate its effect on the output traffic characteristics and network performance under self-similar traffic. Simulation results show that our proposed mechanism can not only effectively reduce the burstiness of input traffic, but also perform better than the non-traffic shaping scheme in the terms of packet-loss rate and blocking probability.

Abstract:The general analytic expression of the chirped sampled function is derived based on coupled mode theory. This function can be used to describe how to use uniform period fiber Bragg grating to produce the equal chirp at will in the specific reflection channel. As an example, the exact sampled function expression that produces a linear chirped at the +4 channel is given. The simulation results by using the transfer-matrix show that the theory is correct. Supported National “863” High Technology Project of China (No. 2003AA311070) and the National Natural Science Foundation of China (No. 60377026).

Abstract:A spatial modulation method for electronic speckle patterns is presented. Carrier fringes are produced by object tilting and the phase field of deformation is demodulated by Fourier transform. The principle is discussed. The system and some typical experimental results are offered. The results prove that by using object tilting method speckle patterns can be modulated very well and the out-of displacement of an object can be obtained effectively.

Abstract:In many image resolution enhancement applications, the blurring process of the imaging system is unknown. This paper discusses the problem of single image blind resolution enhancement without estimating the point spread function (PSF). A regularization model is constructed for image enhancement based on the prior information of image error and image gray value, which does not need any prior information of PSF. Moreover, through the solution of Euler equations, and anisotropic nonlinear diffusion equation are obtained, which can avoid the high computational cost of regularization model. Furthermore, in order to get sub-pixel superresolved image, the regularization model for image enhancement is extended to the enlargement of image, which can enlarge and enhance image at the same time Last, to get clearer edges, a high frequency enhancement filter is used on the superresolved image Numerical results show that the new model can get much clearer super-resolution images than traditional methods, and the peak signal to noise ratios (PSNRs) are also higher than traditional methods. Supported by the National Natural Science Foundation of China (No. 60272013) and National Excellent Doctoral Dissertation Fund of China (No. 200140)

Abstract:In order to evaluate the imaging quality of CCD cameras fully and rapidly, the minimum resolvable contrast (MRC) is presented in this paper and the system of measuring MRC is constructed as well, in which two integrating spheres are proposed to illuminate two sides of the garget respectively. The variable contrast can be obtained by regulating the luminance of integrating spheres. Experimental results indicate that the error of measuring luminance is within ±0.3 cd/m², MRC rises with the increase of the spatial frequency. The experimental results show that the method proposed is an effective approach to evaluate the imaging quality of CCD cameras. Supported by Science and Technology Research Project of Education Department of Heilongjiang Province (10051065)

Abstract:Statistical shape prior model is employed to construct the dynamics in probabilistic contour estimation. By applying principal component analysis, plausible shape samples are efficiently generated to predict contour samples. Based on the shape-dependent dynamics and probabilistic image model, a particle filter is used to estimate the contour with a specific shape. Compared with the deterministic approach with shape information, the proposed method is simple yet more effective in extracting contours from images with shape variations and occlusion.

Abstract:On the basis of the quantization of mesoscopic biological cell equivalent circuit,we studied the quantum fluctuations of voltage and current of mesoscopic biological cell equivalent circuit as finite temperature by Bogoliuov transformation. The result shows that the quantum fluctuations of voltage and current not only relate with the parameters of equivalent circuit, temperature, but also decay with time. This result may have significant value on the design and application of the bio-electronic apparatus.

Abstract:We have analyzed the order-disordering variance due to resonance effect and the nonlinear behavior of far infrared ray laser (FIRL)-biological system interaction. The analytic results show that the interaction between the living biological system and FIRL can produce resonance excitation effect, and so the original high ordered state of the system can be destroyed and thus the conformation variation in the system can be produced under further action of the laser. In addition, we have analyzed the nonlinear properties of the FIRL bio-molecule interaction and explained the mutagenesis effects of FIRL. The theoretic analysis is consistent with the results of FIRL mutagenesis breeding test. This work is supported by National Nature Science Foundation of China (No. 60068001 and No. 30360068) and the NSFYP (No. 2000A0021M)

Abstract:

Abstract: