An adaptive controller for a class of nonlinear system using direction basis function

For a class of nonlinear dynamical systems, the adaptive controllers are investigated using direction basis function (DBF) in this paper. Based on the criterion of Lyapunov' stability, DBF is designed which guarantees that the output of the controlled system asymptotically tracks the reference signals. Finally, the simulation shows the good tracking effectiveness of the adaptive controller.

Thermally stable chromophores for nonlinear optical applications

Three thermal organic second-order nonlinear optical chromophores were synthesized. The decomposition temperature was determined by DSC, and the absorption spectra was measured. The second-order polarizabilities at zero energy and the dispersion of second-order polarizabilities were measured by solvatochromic method. (C) 2002 Elsevier Science Ltd. All rights reserved.

Investigation on the nonlinear optical properties of the DCNP/PEK-c guest-host polymer films

The polyetherketone (PEK-c) guest-host polymer thin films doped with 3-(1,1-dicyanothenyl)-1-phenyl-4,5-dihydro-1H-pryazole (DCNP) were prepared. The polymer films were investigated with in situ second-harmonic generation (SHG) measurement. The corona poling temperature was optimized by the temperature dependence of the in situ SHG signal intensity under the poling electric field applying. The temporal and temperature stability of the second-order properties of the poled polymer film were measured by the in situ SHG signal intensity probing. The second-order NLO coefficient chi ((2))(33) = 32.65 pm/V at lambda = 1064 nm was determined by using the Makel fringe method after poling under the optimal poling condition. The dispersion of the NLO coefficient of the guest-host polymer system was determined by the measured value of chi ((2))(33) at 1064 nm and the two-level model.

Effect of the electrostatic interactions of chromophores on the macroscopic second-order nonlinear optical properties of the polymer films

The polyetherketone (PEK-c) guest-host system thin films doped with 3-(1,1-dicyanothenyl)-1-phenyl-4,5-dihydro-1H-pryazole (DCNP) were prepared. Their second-order nonlinear optical (NLO) coefficients chi(33)((2)) were measured by using Maker fringe method for the polymer films doped with different weight percents of DCNP. Experimental results indicate that the second-order NLO properties of the poled polymer films could decrease with the chromophore loading increasing when the chromophore loading reaches a fairly high level. In this paper, the relationship between the macroscopic second-order NLO coefficient and the chromophore number density was modified under considering the role of the electrostatic interactions of chromophores in the polymer film. According to the modified relationship, the macroscopic second-order NLO coefficient is no longer in direct proportion with the chromophore number density in the polymer film. The effect of the electrostatic interactions of chromophores on second-order NLO properties was discussed. The attenuation of the macroscopic second-order NLO activity can be demonstrated by the role of the chromophore electrostatic interactions at high loading of chromophore in the polymer systems.

Refractive index dispersion measurement on nonlinear optical polymer using V-prism refractometer

By using V-prism refractometer, the refractive indices of a polyetherketone (PEK-c) guest-host polymer system were measured with the polymer in solutions. The Lorenz-Lorentz local field formalism was used in the calculation of the refractive indices of the polymers from the measured indices of the polymer solutions and the pure solvent by using V-prism refractometer. The refractive index dispersions of the polymers were obtained by fitting the measured indices of the polymers to Sellmeyer equation. The method allows for an accuracy in index of 0.7% in the determination of the polymer indices. In addition, a large difference between the indices of the polymer and the solvent, and a higher polymer volume fraction in the measured polymer solution are favorable for a high accuracy. (C) 2000 Elsevier Science Ltd. All rights reserved.

Linear and nonlinear intersubband optical properties in a step quantum well with an applied electric field

Within the framework of the effective-mass envelope-function theory, the field-dependent intersubband optical properties of a Al0.4Ga0.6As/Al0.2Ga0.8As/GaAs step quantum well are investigated theoretically based on the periodic boundary condition. A very large Stark shift occurs when the lowest subband electron remains confined to the small well while the higher subband electron confined to the big well. The optical nonlinearity in a step well due to resonant intersubband transition (ISBT) is analyzed using a density-matrix approach. The second-harmonic generation coefficient chi(2 omega)((2)) and nonlinear optical rectification chi(0)((2)) have also been investigated theoretically. The results show that the ISBT in a step well can generate very large second order optical nonlinearities, chi(0)((2)) and chi(2 omega)((2)) can be tuned by the electric field over a wide range.

Color filter-less technology of LED back light for LCD-TV - art. no. 68410G

Back Light Unit (BLU) and Color Filter are the two key components for the perfect color display of Liquid Crystal Display (LCD) device. LCD can not light actively itself, so a form of illumination, Back Light Unit is needed for its display. The color filter which consists of RGB primary colors, is used to generate three basic colors for LCD display. Traditional CCFL back light source has several disadvantages, while LED back light technology makes LCD obtain quite higher display quality than the CCFL back light. LCD device based on LED back light owns promoted efficiency of display. Moreover it can generate color gamut above 100% of the NTSC specification. Especially, we put forward an idea of Color Filter-Less technology that we design a film which is patterned of red and green emitting phosphors, then make it be excited by a blue light LED panel we fabricate, for its special emitting mechanism, this film can emit RGB basic color, therefore replace the color filter of LCD device. This frame typically benefits for lighting uniformity and provide pretty high light utilization ratio. Also simplifies back light structure thus cut down the expenses.

Ultra-compact silicon-on-insulator optical filter based on sidewall Bragg grating

Micro-cavity structure composed of silicon wire with 240nm square cross section and two symmetrical sidewall waveguide Bragg gratings is fabricated and studied for the operation under telecommunication wavelengths. Optical filter of quasi-TE mode was realized based on this cavity. In such micro-cavity, optical quality factor (Q) was measured up to 380 with a 4.8nm free spectral range (FSR) and 12dB fringe contrast (FC). The measured group index of silicon waveguide with only 240nm square cross section was between 3.80 and 5.43. It is the first time group delay of silicon wire waveguide with such small core dimension is studied. Larger group delay can be expected after optimizing the design parameters and the fabrication process.

Design of Low Power Multi-Standard Active-RC Filter for WLAN and DVB-H

In this paper, a low-power, highly linear, integrated, active-RC filter exhibiting a multi-standard (IEEE 802.11a/b/g and DVB-H) application and bandwidth (3MHz, 4MHz, 9.5MHz) is present. The filter exploits digitally-controlled polysilicon resister banks and an accurate automatic tuning scheme to account for process and temperature variations. The automatic frequency calibration scheme provides better than 3% corner frequency accuracy. The Butterworth filter is design for receiver (WLAN and DVB-H mode) and transmitter (WLAN mode). The filter dissipation is 3.4 mA in RX mode and 2.3 mA (only for one path) in TX mode from 2.85-V supply. The dissipation of calibration consumes 2mA. The circuit has been fabricated in a 0.35um 47-GHz SiGe BiCMOS technology, the receiver and transmitter occupy 0.28-mm(2) and 0.16-mm(2) (calibration circuit excluded), respectively.

Simulation and fabrication of the SiC-based clamped-clamped filter

In this paper, the SiC-based clamped-clamped filter was designed and fabricated. The filter was composed of two clamped-clamped beam micromechanical resonators coupled by a spring coupling beam. Structural geometries, including the length and width of the resonator beam and coupling beam, were optimized by simulation for high frequency and high Q, under the material properties of SiC. The vibrating modes for the designed filter structure were analyzed by finite element analysis (FEA) method. For the optimized structure, the geometries of resonator beams and coupling beams, as well as the coupling position, the SiC-based clamped-clamped filter was fabricated by surface micromaching technology.

Design and Fabrication of a Photonic Crystal Channel Drop Filter Based on an Asymmetric Silicon-on-Insulator Slab

We report on the design and fabrication of a photonic crystal (PC) channel drop filter based on an asymmetric silicon-on-insulator (SOI) slab. The filter is composed of two symmetric stick-shape micro-cavities between two single-line-defect (W1) waveguides in a triangular lattice, and the phase matching condition for the filter to improve the drop efficiency is satisfied by modifying the positions and radii of the air holes around the micro-cavities. A sample is then fabricated by using electron beam lithography (EBL) and inductively coupled plasma (ICP) etching processes. The measured 0 factor of the filter is about 1140, and the drop efficiency is estimated to be 73% +/- 5% by fitting the transmission spectrum.

The structure and function of neurons with variable nonlinear transfer function

One novel neuron with variable nonlinear transfer function is firstly proposed, It could also be called as subsection transfer function neuron. With different transfer function components, by virtue of multi-thresholded, the variable transfer function neuron switch on among different nonlinear excitated state. And the comparison of output's transfer characteristics between it and single-thresholded neuron will be illustrated, with some practical application experiments on Bi-level logic operation, at last the simple comparison with conventional BP, RBF, and even DBF NN is taken to expect the development foreground on the variable neuron.. The novel nonlinear transfer function neuron could implement the random nonlinear mapping relationship between input layer and output layer, which could make variable transfer function neuron have one much wider applications on lots of reseach realm such as function approximation pattern recognition data compress and so on.

High-Q and High-extinction-ratio Microdisk Add-drop Filter with Grating Couplers in Silicon-on-Insulator

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Adaptive fading Kalman filter with an application

A new adaptive state estimation algorithm, namely adaptive fading Kalman filter (AFKF), is proposed to solve the divergence problem of Kalman filter. A criterion function is constructed to measure the optimality of Kalman filter. The forgetting factor in AFKF is adaptively adjusted by minimizing the defined criterion function using measured outputs. The algorithm remains convergent and tends to be optimal in the presence of model errors. It has been successfully applied to the headbox of a paper-making machine for state estimation.