Si nanoparticles are synthesized at a high rate (400–500 mg/h) using the perpendicular pulsed laser ablation (PPLA) on the silicon target at room temperature in Ar atmosphere. The PPLA method can also be used to obtain Si nanocrystal films with large areas on the glass substrate. These particles are etched with a mixture of hydrofluoric acid (HF) and nitric acid (HNO3) to reduce their sizes and the surfaces of these particles are passivated by the high-pressure water vapor annealing (HWA). After treating the particles exhibit blue emission (with maximum photoluminescence (PL) intensity at 404 nm) at room temperature.
Based on the theory of one-dimensional photonic crystal, an asymmetrical interleaver filter composed of thin-film glass cavities is designed. Three thin-film glass cavities are cascaded in the structure. Each cavity is formed by evaporating several layers of reflecting films on two surfaces of the glass medium. Compared with other proposed structures, this interleaver filter is very simple and easy to realize, and it has flat passband and stopband. A design example of a 50 GHz interleaver filter with the duty cycle of 1:5 is presented. The influence of the structural parameters of each reflecting film (including the glass cavity) on the spectral performance is discussed. And the design results with duty cycles of 1:3 and 1: 4 are also shown and analyzed.
The exact solution of time-evolution operator is obtained by applying the gauge transformation of algebra dynamics. Such an operator describes the time-evolution of the quantum state for two inductance coupled mesoscopic LC circuits. The zero-state responses of the charge and current to the input voltage signal are calculated. The results show that the system of inductance coupled mesoscopic LC circuits is linear and time-invariant. The zero-state responses of the charge and current are consistent with those of the corresponding macroscopic circuit.
The switchable dual-wavelength erbium-doped fiber laser (EDFL) with a two-mode photonic crystal fiber (PCF) loop mirror and a chirped fiber Bragg grating (CFBG) at room temperature is proposed and experimentally demonstrated. The two-mode PCF loop mirror is formed by inserting a piece of two-mode PCF into a Sagnac loop mirror, with the air-holes of the PCF intentionally collapsing at the splices. By adjusting the state of the polarization controller (PC) appropriately, the laser can be switched between the stable single- and dual-wavelength operations by means of the polarization hole burning (PHB) and spectral hole burning (SHB) effects.
The characteristics of fiber Bragg gratings (FBG) at local temperature are investigated based on the transfer matrix method. The reflective spectrum model of the FBG at local temperature is analyzed by theoretics and simulations. The results show that when a small section of the FBG is affected by the temperature variation, the reflective spectrum splits into two main peaks. The wavelength of the splitting point shifts linearly and periodically with the local temperature on the FBG. An experiment is also presented, and its results are agreement with the simulations.
The effects of the cathode operation voltage, the absorption coefficient, the carrier mobility, the temperature and the thickness of organic active layer on the short-circuit current density of single layer organic solar cells (OSCs) with Schottkey contacts are numerically studied. Quantitative dependences of the short-circuit current density on the respective parameters are obtained. The results show that a larger operation-voltage difference between the anode and the cathode, a higher carrier mobility as well as a thinner organic layer thickness are of great benefit to the increase of the short-circuit current density.
The performance of amorphous silicon (a-Si:H) / crystalline silicon (c-Si) heterojunction is studied, and the effects of the emitter layer thickness, doping concentration, intrinsic layer thickness, back heavily-doped n layer, interface state and band offset on the optical and electrical performance of bifacial heterojunction with intrinsic thin-layer (HIT) solar cells on ntype silicon substrates are discussed. It is found that the HIT solar cells on n-type substrates can obtain a higher conversion efficiency than those on p-type substrates by calculating the band diagrams and parameters of HIT solar cells.
The AC driving scheme for OLEDs, which uses the pixel circuit with two transistors and one capacitor (2T1C), can extend the lifetime of the active matrix organic light-emitting diode (AMOLED) on silicon, but there are switching effects during the switch of AC signals, which result in the voltage variation on the storage capacitor and cause the current glitch in OLED. That would decrease the gray scale of the OLED. This paper proposes a novel pixel circuit consisting of three transistors and one capacitor to realize AC driving for the OLED-on-silicon while restraining the switching effects. Simulation results indicate that the proposed circuit is less sensitive to switching effects. Also, another pixel circuit is proposed to further reduce the driving current to meet the current constraints for the OLED-on-silicon.
Precisely adjusting the color purity of LaAlO3:Eu3+ red phosphor with 593 and 618 nm emissions is achieved in a strategy of suppressing transitions of high energy levels of Eu3+ ions through varying the doping concentration. As the doping concentration increases, the transitions from high levels 5D3,2,1 will be weakened, while those from 5D0 are enhanced up to a critical value with the aid of the cross relaxation. As a result, an increase of the color purity from 95.2% to 97.4% is obtained. It indicates that the red phosphor could be one of the excellent red-light-emitting phosphors in illuminating and display devices.
The improved Fourier transform profilometry (IFTP) and phase-shifting profilometry (PSP) are typical phase calculation methods in 3D optical phase measurement. The PSP has a high ability of anti-noise, but the projective grating needs a spatial frequency as high as possible, so that the wrapped phase results in superposition due to undersampling. IFTP expands measuring range, but the loss of high frequency component in the wrapped phase would cause a fast change of phase. Considering the advantages and disadvantages of IFTP and PSP, a new algorithm which combines the two methods is proposed to improve the accuracy of phase calculation. The simulation and experimental results demonstrate that this algorithm possesses better anti-noise performance. By means of this method, a better result for phase calculation is obtained over IFTP and PSP.
In this paper, a digitized real-time demodulation system for optical hydrophones based on a 3 × 3 coupler is proposed. The system is built as a virtual instrument via the dynamic data acquisition platform from NI company. Compared with the commonly used systems composed of analogue circuits, the proposed system has better accuracy and is more flexible in applications. The error analysis of the proposed system is also given.
To solve the problem that using only one feature is poor for the terrestrial environment classification, a new feature fusion method at decision level is proposed in this paper. An eigenvector is obtained by using a Gaussian mixture model (GMM) firstly, and the probabilities of the eigenvector belonging to a certain class of the texture and color are computed. Then the probabilities are multiplied by different weights according to the contribution, and summed to get the maximal likelihood probability to achieve feature fusion. Experimental results demonstrate that the method in this paper is better than other current methods and the classification performance is superior to a single feature obviously.
Aiming at the serious interference of the cross term existing in the time-frequency (TF) filtering method, an adaptive TF filtering method for nonstationary signals based on the generalized S-transform is proposed. Firstly the time-frequency distribution spectrum of the signal is got by the generalized S-transform, then the clustered energy of the signal on the time-frequency plane is identified by the TF region extraction algorithm, thirdly the TF filtering factor is constructed based on the distribution characteristic of the effective signal and noise, and finally the random noise is removed from the original signal and the effective signal is remained. Simulation results demonstrate that this method has satisfactory performance in denoising and improving the signal-to-noise ratio.
A combined object-tracking algorithm that realizes the realtime tracking of the selected object through the omni-directional vision with a fisheye lens is presented. The new method combines the modified continuously adaptive mean shift algorithm with the Kalman filter method. With the proposed method, the object-tracking problem when the object reappears after being sheltered completely or moving out of the field of view is solved. The experimental results perform well, and the algorithm proposed here improves the robustness and accuracy of the tracking in the omni-directional vision.
Under the condition of resonance, the entanglement of field-atom is investigated using the quantum reduced entropy. The effects of the initial field intensity, the interaction intensity between the optical field and atoms and that among Bose-Einstein condensate (BEC) atoms on the evolution of the quantum entanglement are discussed. The results indicate that when the strength of the light field is strong enough, the system of the Schro-dinger cat state optical field interacting with BEC atoms is always at the entangled state.
The preparation and transfer of entanglement in atomic ensembles interacting with cavity fields is investigated. The results show that two pairs of quasi-Bell states (entangled coherent states) between two atomic ensembles can be explicitly generated through quasi-Bell measurements on cavity fields. It is also indicated that the quantum entanglement between two cavity fields can be perfectly transferred into two atomic ensembles.
The focusing properties of a partially coherent and partially polarized beam focused by a high numerical aperture (NA) objective are investigated. The influence of the degree of polarization and the correlation length of the incident beam and the numerical aperture of the objective on the intensity and degree of polarization in the focal region is studied. It is shown that the intensity and degree of polarization in the focal region change with the degree of polarization and the correlation length of the incident beam.
The optical Bloch equations (OBEs), describing the interaction between the atom and the light field in an inhomogeneously broadened two-level system, are solved by a numerical procedure, which uses an implicit fourth-order Runge-Kutta (RK4) method.Then the properties of the two-pulse photon echo signal are analyzed. The numerical simulation results show that the two-pulse photon echo signal can be strongly modulated by the inhomogeneous linewidth (IL) for the system. In comparison with the classical solution derived under approximate conditions, the highest-intensity photon echo requires the first input pulse area to be greater than 0.5 π for the bigger IL. The attenuation characteristics of photon echo intensity are also calculated and discussed.
The effect of detuning on the few-cycle laser pulse propagation in the ladder-type three-level atomic medium is investigated by using the numerical solution from the Maxwell-Bloch equations without the slowly varying envelope and rotating-wave approximations. The results show that in the resonance case, the obvious variation of the pulse form, including the carrierenvelope phase, the pulse duration, the oscillation amplitude and frequency, even the pulse splitting will occur in the propagation, and the output pulse is much different from the input. In the off-resonance case, the varying detuning also can lead to the considerable variation of the pulse form in the propagation. However, with an appropriate detuning, the selfinduced transparency can be realized, and the output pulse exactly the same as the input can be obtained.