By employing 2D plane wave expansion (PWE) and finite difference time domain (FDTD) methods, a photonic crystal waveguide (PCW) based on the compound square lattice structure is presented. Band-gap can be observed for TM polarization and compared with the simple lattice structure based on the same material, the band-gap is increased by 62.7%. By optimizing the parameters we get the PCW with the propagation only near the wavelength of 1.55 µm and a flat group index curve in a wide wavelength range of 40 nm. And the group velocity dispersion compensation can be realized by the structure optimization. The results provide a reference for the study and application of photonic crystal waveguide based on the compound lattice structure.
A new method, named as doctor-blading, is presented to fabricate light waveguides in electro-optical printed circuit board (EOPCB). This new technology is proven to be suitable for the fabrication of the large size waveguides. The performance parameters of the light waveguides fabricated by the proposed method as well as the influence of the parameters on the performance of the waveguides are analyzed and simulated. The results demonstrate the feasibility of the method to fabricate the polymer waveguides.
Aiming at the problem of luminance uniformity for organic lighting-emitting diode (OLED) panels, a new brightness calculating method based on bilinear interpolation is proposed. The irradiance time of each pixel reaching the same luminance is figured out by Matlab. Adopting the 64×32-pixel, single color and passive matrix OLED panel as adjusting luminance uniformity panel, a new circuit compensating scheme based on FPGA is designed. VHDL is used to make each pixel’s irradiance time in one frame period written in program. The irradiance brightness is controlled by changing its irradiance time, and finally, luminance compensation of the panel is realized. The simulation result indicates that the design is reasonable.
In order to realize the energy saving of the backlight in liquid crystal display (LCD) with approximate image quality, a human visual characteristics guided backlight luminance scaling method is proposed for power minimization. Image histogram clipping and extension steps are firstly established based on the luminance consistency theory. Dark and bright regions of the image are weighted respectively based on the human visual threshold property and then the histogram is clipped to the restricted range. To compensate the degrading of the backlight, visual attention architecture is then imported to extend the histogram nonlinearly and assign the complex image region with a larger weight. Experimental results show that the algorithm can save about 50% backlight energy with 5% image distortion.
Because the polarization effect influences the distribution of the carriers in the multiple quantum wells of the light-emitting diodes (LEDs), the light-emitting efficiency is also affected. The influence of the polarization effect on GaN-based LEDs’ performance is simulated. By simulating four different types of electrode shapes, it’s found that the electrode shape influences not only the photoelectric characteristics but also the optical absorption by the semiconductor. Through the optimization of the electrode shape, the I–V characteristic is improved, and the series resistance is lowered. The optical absorption by the semiconductor is decreased and then the heat generated in the LEDs is lowered. As a result, both the photoelectric conversion efficiency and the stability are improved.
The low power design of a field sequential color (FSC) liquid crystal on silicon (LCoS) chip for near-to-eye application is presented in this paper. Dual power supplies are used in the design, that is, the supply for part of driving circuits is 3.3 V, and the one for the active matrix is 5.0 V. Serial-to-parallel conversion circuits are adopted to lower the pixel clock frequency of the chip. Also, an idle state is inserted into the pixel clock signal to decrease the switching activity factor to further reduce the power consumption. The LCoS chip is fabricated with 0.35 µm CMOS process and its power consumption is only about 300 mW.
A novel optoelectronic oscillator (OEO) based on dual-lasers is demonstrated in this paper. The oscillator takes advantage of the dual optical fiber loops with different mode separations, which induces the gain competition and leads to high side-mode suppressed ratio (SMSR). Besides, the OEO can also suppress the random interference and the beating noise when single laser source is used. Finally, the results are as follows: the operating frequency is 4.998 GHz, the phase noise is 113 dBc/Hz at 10 kHz, the SMSR is more than 60 dB, and the time jitter is 289 fs.
A novel fiber Bragg grating (FBG) current sensor with temperature compensation has been proposed. The fiber Bragg grating is glued on the surface of an isosceles triangle cantilever beam, which has a step thickness along the beam axis. Due to the electromagnetic force created by a solenoid and a permanent magnet mounted on the top of the beam, a step strain is applied on the fiber Bragg grating. The change of the electric current in the solenoid makes the spectrum of the fiber Bragg grating split. By monitoring the shift difference of the two split center wavelengths, which is related to the electric current in the solenoid, a current sensor with temperature compensation is obtained. The test range of 0–400 mA is achieved. The experimental results also show that the relationship between the shift difference of the two split center wavelengths of the FBG and the electric current has a linearity of 0.9937, and the sensitivity is about 2.64 nm/A; the test results are independent of the temperature, so the cross sensitive problem is solved.
By using the transfer matrix, the band structures, defect mode and field propagation characteristics of one-dimensional photonic crystals composed of single-negative (SNG) material are studied. It is shown that this structure possesses a new type of photonic gap which is insensitive to the incident angle and the light polarizations, as well the change of scale length. When a normal dielectric defect layer is inserted, the defect mode is insensitive to the angle of incidence, but the electromagnetic field in the defect layer is strongly localized, and the number of the defect modes increases with the thickness of the defect layer.
The free-standing diamond films are deposited on molybdenum substrate by direct current jet chemical vapor deposition (DCJCVD). X-ray diffraction, Raman spectroscopy and cathodoluminescence (CL) measurement are used to investigate the films structure and defects related to electron transition properties of the diamond films. The X-ray diffraction spectrum reveals that the diamond films have the polycrystalline cubic structure with diffraction peaks at 43.88° and 75.24°. A sharp peak at 1331.8 cm−1 and a broad band at about 1250–1550 cm−1 from Raman spectrum are attributed to diamond phase and sp2-type carbons, respectively. Two emission peaks at 440 nm and 530 nm, associated with dislocation defects and nitrogen and vacancy complexes respectively, are observed in cathodoluminescence spectrum. In addition, in order to understand both emission processes, a simple energy level scheme is suggested.
To improve the current status of home multilayer optical coating design with low speed and poor efficiency when a large layer number occurs, the accurate calculation and fast realization of merit function’s gradient and Hesse matrix is pointed out. Based on the matrix method to calculate the spectral properties of multilayer optical coating, an analytic model is established theoretically. And the corresponding accurate and fast computation is successfully achieved by programming with Matlab. Theoretical and simulated results indicate that this model is mathematically strict and accurate, and its maximal precision can reach floating-point operations in the computer, with short time and fast speed. Thus it is very suitable to improve the optimal search speed and efficiency of local optimization methods based on the derivatives of merit function. It has outstanding performance in multilayer optical coating design with a large layer number.
The noise in polymer optical amplifiers is mainly derived from the amplification of spontaneous emission (ASE). In this paper, the noise characteristic of dye-doped polymer optical fiber amplifiers is studied. The propagation equations of ASE power and the rate equations of dye molecular concentration are found based on the energy level transition of dye. The noise characteristic of optical fiber amplifiers is given by solving above equations numerically, and the relationship between noise figure and parameters of optical fiber amplifiers is investigated in detail. The result shows that the noise figure of dye-doped polymer optical fiber amplifiers will not exceed 5 dB.
In order to decrease the blocking probability of fast light-path set-up in the network, a novel strategy for optical flow switching is proposed, named dynamically initialized wavelength number protocol (DIWP), which can dynamically change the initialized wavelength number according to the traffic load of the network. Computer simulations are conducted to analyze the performance of the proposed strategy, which is based on forward reservation backward release (FRBR) mechanism. The results show that the initialized wavelength number can affect the blocking probability of the network.
A new kind of two-dimensional optical orthogonal code named ESPC/OCS is constructed, which uses the extend square prime code (ESPC) for time spreading and the one-coincidence sequence(OCS) for wavelength hopping. The performance of ESPC/OCS is analyzed and the mean value of cross-correlation is deduced. Meanwhile the bit error ratio (BER) for codes is simulated and compared. The simulation results show that given p and q, the BER of ESPC/OCS is reduced, and the capacity is enlarged, when the number of hopping codes p is increased. Given OCS (given q and d), when p is changed, only the capacity is changed, but the BER is almost the same. The performance of ESPC/OCS is better than that of PC/OCS.
To lower the bit error rate (BER) of the pulse position width modulation (PPM+PWM), which is the improved scheme of the pulse position modulation (PPM), correcting coding technique is necessary. After setting up the analytic model, the Turbo decoder and iterative algorithm for PPM+PWM are studied, and the system error performance of uncoded and Turbo coded PPM+PWM under the Gaussian channel is simulated and analyzed, as well as the effects of the number of iterations and frame size on the bit error rate. The results show that the introduction of Turbo code can get the encoding gain of 4.0–6.9 dB, which improves the error performance of system effectively and has advantage in military communications.
The design and implementation of FPGA-and-USB-based control board for quantum experiments are discussed. The usage of quantum true random number generator, control- logic in FPGA and communication with computer through USB protocol are proposed in this paper. Programmable controlled signal input and output ports are implemented. The error-detections of data frame header and frame length are designed. This board has been used in our decoy-state based quantum key distribution (QKD) system successfully.
A novel method for laser beam straightness error measurements based on common-path compensation is proposed. The basic principle of the method is described and the math-model is established. Furthermore, the influence of laser beam drift on straightness error measurements is analyzed. The experimental results show that the measurement accuracy can be greatly improved by using the common-path compensation for laser beam drift.
Rotation, scaling and translation (RST) attacks can desynchronize the watermark detection so that many watermark systems failed. A geometrically robust image watermarking strategy based on Jacobi-Fourier moments (JFMs) is proposed. The Jacobi moments of the original image are first extracted as original moments; then the watermark image is embedded into the global or local area of the original image, and the Jacobi moments of the area are extracted. When the watermarked image is not attacked, the watermark can be retrieved by using the margin of the original moments and the moments of the embedded area. When it is attacked, the watermark can also be got in that way, and the original moments need to be transformed. It can be concluded that Jacobi-Fourier moments perform better than Zernike moments (ZMs) for small images. Meanwhile, the watermark is also robust to scaling and rotation as well as regular attacks such as added noises.
In order to solve the ordered quantum database search problem, a quantum binary searching algorithm was proposed which can be used to implement the whole searching process in four steps. Considering the characteristic of quantum parallelism, this paper further improves the searching process, which can be realized in only two steps, and presents the circuit implementation. In this scheme, the number of the quantum logic gates doesn’t increase. Moreover, the losing-solution issue in the quantum binary searching algorithm can be efficiently prevented.
An improved scheme for passive synthetic aperture imaging is proposed. With this new technique, the radiation signal from field of view (FOV) is received and its frequency is down-converted to intermediate frequency (IF). The IF signals are modulated to light-wave by electro-optical phase modulators and transmitted in fiber. At the end of the fiber, a downscaled fiber array is formed according to the receiver array. The image of FOV is obtained with the fiber array. The principles of passive synthetic aperture photonic imaging technique are analyzed deeply and its properties are compared with traditional imaging method of synthetic aperture. By simulation, the spread function of spot source and the image signal-noise-ratio are investigated using the new imaging approach with FOV radiation from different incidence angles. The introduced scheme can reconstruct the target image and perfect the present synthetic aperture imaging systems.
Randomized Hough transform (RHT) is an effective method for circle detection. But when dealing with multi-circle complex images, the random sampling will bring lots of invalid accumulations and result in a large number of calculations. In this paper, by selecting three points of the candidate circle, a fast detection algorithm of multi-circle with randomized Hough transform is presented. Experimental results demonstrate that the proposed scheme can quickly detect multiple circles, and has a strong robustness.