The photoionization/photodissociation mechanism of allyl chloride was investigated with a 50 fs laser pulse at 200, 400 and 800 nm. With the ionization mass spectra and light intensity index recorded at three different wavelengths, the dependence of strength of the parent and fragment ions with the wavelength was analyzed. It was found that the parent ion (C3 H5 Cl + ) comes from directly non-resonance ionization with 200 nm femtosecond pulse, while the daughter ions are from dissociative ionization of C3 H5 Cl + . At 400 nm, some molecules are excited to the high Rydberg state and C3 H5 radicals are generated by direct dissociation. The enhancement of C3 H + 5 signal is observed since multi-photon ionization of C3 H5 increases the population of C3 H + 5. At 800 nm, nσ states and some Rydberg states are both populated. The further increased population of C3 H5 leads to an increase of C3 H + 5. The wavelength dependence of C3 H + 4 yield is less pronounced, since it comes from dissociative ionization of C3 H + 5 and C3 H5 Cl + .
The electric field direction control characteristics of one-dimensional ladder-type double-period fourth generation quasi-periodic structure defect modes with nematic liquid crystal defect layer was studied by transmission matrix method. Relationship between θ, angle of the applied electric field and incident wave direction, and position of defect mode wavelength, quality factor, optical field distribution of spatial position were analyzed. The influence of quality factors of defect modes on light field intensity was discussed. Results show that the positions of defect modes shift to short wave direction with increasing of θ, and the regulation amount of defect modes wavelength is 84 nm. The quality factors of defect modes increase gradually with increasing of θ. The optical field distribution of defect modes exhibit local phenomenon in spatial location. The light field strength of spatial location is gradually enhanced with increasing of θ. Quality factors of defect modes are proportional to the light field strength.
Considering the problems of low contrast and color distortion caused by scattering and attenuation of the light in underwater environment, the underwater color image enhancement method was presented, which integrated dark channel prior and the color correction algorithm based on channel histogram quantization. For the underwater color image to be enhanced, underwater optical imaging model was established and the optimized and improved dark channel prior algorithm was used for image deblurring. By analyzing the cumulative histogram of the deblurring image R, G, B three channels, the gray value of each channel was quantified to achieve color correction of the image. The experimental results show that the proposed method can effectively eliminate the image blur caused by scattering of light, improve the visual quality of the underwater image and restore color balance of the image.
There were a large number of studies about the influence of the speckle statistical characteristics on single pixel imaging system, but effect of speckle density on the system was not reported. The scene images of 1 bit and 8 bits were studied by computer simulation, and the results show that the quality of the recovered images will be better with increasing of sample number. In the case of 1 bit image, the quality of the recovered image will be good and then poor with increasing of speckle density, and the best image can be obtained in the middle value of speckle density. However, for 8 bits image, when the sample number of speckle is small, quality of the recovered image will be good and then poor with increasing of speckle density, and vice versa. The more speckles are employed, the better recovered image can be obtained. However, it can reduce efficiency of the single pixel imaging system. The research of speckle density provides a good reference to overcome this shortcoming, and has certain practical application value.
In order to solve the defect such as low forgery detection precision and difficult to detect small tampered area induced by color interpolation noise which resulting in low resolution because of using the color filter array (CFA) in current image forgery location technologies, the copy-move image forgery detection algorithm based on pixel prediction error coupled likelihood mapping was proposed. The green component was extracted from the image based on analysis of CFA. The prediction error and its local weighted variance model were constructed by embedding the weight factor, and the function of false feature statistics was defined by prediction error and Bayes theory to identify the feature value tending to zero. The likelihood ratio of this feature function was built by the feature statistical model to output forgery mapping for finishing the detection. Simulation results show that this algorithm has better robustness to identify small false pixels, as well as higher AUC value and ideal ROC curve.
A novel physical model was proposed to describe silicon-on-insulator (SOI) waveguide Raman lasers by considering the spontaneous Raman scattering effect in cavity. Numerical results show that the proposed model can well describe small-signal output characteristics of SOI waveguide Raman lasers and realize rapid analysis, design and improvement on them. The SOI waveguide Raman lasers were analyzed using the model. Results indicate that the key to reach the laser thresholds in room temperature is a SOI waveguide with large Raman coefficient, low loss, and short effective free carrier lifetime. By optimizing the transverse geometric size, a high overall Raman gain can be achieved in SOI waveguides with short effective carrier lifetime, which can increase the output power and conversion efficiency of SOI waveguide Raman lasers.
The precisely controlled spectral characteristics of a novel Sagnac loop filter was studied, which is structured by insertting two segments of high birefringence optical fiber and a fiber polarization controller into a conventional optical fiber Sagnac loop filter. The filtering characteristics of the filter was investigated theoretically by using the equivalent optical-path analysis and transfer matrix method. Results show that when the birefringence parameters of fiber are fixed, the spectral characteristics of the Sagnac loop filter can be precisely controlled by changing the polarization controller status. The Sagnac loop filter can be used to flat the spectra of erbium-doped fiber (EDF) amplified spontaneous emission (ASE) light source, and the broadband ASE laser with flat spectra is obtained in experiment by controlling the tilt angle of the three waveplates of polarization controller.
A scheme was proposed that the five particle cluster state shared by three parties functions as the quantum channel for the two-way teleportation of a single particle, in which the two communicating parties Alice and Bob each have two particles of the five particle cluster state and the particles A and B of the unknown single particle state, and the controller Cindy has one particle of the five particle cluster state. To start with, Alice and Bob have to perform respectively Bell-state measurements of the particle A and B in their hands and the one particle in the channel, informing each other plus the controller Cindy of the measurement through the classical channel. Then, Cindy has to conduct single-particle projective measurement of one particle that she has, notifying the measurement results of Alice and Bob in the same way. Based on the measurement of the three parties Alice and Bob have to make their own appropriate unitary operations of another particle so that they can get the quantum state that they are sending to each other, helping to achieve the aim of the controlled two-way teleportation of single particle state.
The botnet needs to maintain periodic communication between the controller and compromised hosts, so it becomes possible to utilize the periodic communication to achieve the botnet detection. Although some algorithms were proposed to achieve the botnet detection based on the periodic communication behavior, it is still a problem how to achieve the faster detection of botnet in the vast amounts of data. The improved detection algorithm introduces quantum computing into accelerating the periodic communication detection based on the existing algorithm. The experimental results show that the improved algorithm owns the same accuracy compared with existing algorithms, and all abnormal IP can be detected correctly. Meanwhile, it can utilize the less query count to complete the detection of botnet, and effectively achieve the algorithm acceleration.
Quantum key distribution (QKD) is a research topic of information security area. It can provide physical security key distribution. However, the low key rate of QKD limits its practical appliance. The increasement of the speed of LD driver pulse modulation effectively improves signal rate, to expedite the key generation rate of quantum key distribution. Modulation rate of 200 MHz can be achieved based on FPGA at 200 MHz clock frequency. Experiment results show that the jitter of the output quantum signal is less than 2 ns when using the scheme to generate trigger pulse to driving LD, which meets the requirements of quantum key distribution.
Traditional email business uses the plain text to transfer the mail content. If the eavesdropper captures the data packets and owns enough computing capability, he will easily analyze the data. Therefore the data might be leaked. Although there are some solutions that could increase the security performance of email, the insecurity factors still remain. To solve the above problem, a quantum mail transfer system is proposed to transfer the main data based on quantum channel. Combining quantum channel with traditional channel and establishing quantum SMTP protocol, POP3 protocol in email transportation process insure email security. The simulation analysis showed that the exposed probability of quantum email is closer to 0 when the length of mail data is near to 30 bit. So, even if the eavesdropper owns enough computing, the quantum mail transfer system owns better secure performance.
Various correlations in system of single Jaynes-Cummings (J-C) atom and an isolated atom were investigated via the measurement of geometric quantum discord proposed by Dakic et al. The dynamical evolutions of geometric quantum discord between two atoms were numerically analyzed as well as those of the quantum entanglement and quantum discord. Results show that quantum correlations can be increased by increasing initial entanglement and purity of the prepared W-state of the two atoms. The coupling constant and photon number play significant roles in the quantum correlation dynamics.
By numerical calculation, the quantum correlation dynamics of two moving atoms was investigated in Tavis-Cummings model in which the two moving atoms interact with the particle field. The effects of the initial entanglement of the two atoms and the number of photon in the particle field and atomic movement on entanglement and quantum discord were analyzed. The results show that initial entanglement is different, and the time evolution of atoms’ quantum entanglement and quantum discord is different. With the increase of the number of photon, phenomenon of sudden death and birth of quantum entanglement between two atoms occurs, while quantum discord keeps nonzero and the time evolution of quantum entanglement and quantum discord becomes faster. Atomic movement can make quantum entanglement and quantum discord has a periodic evolution. The increase of the field model structure parameter can make the period of quantum entanglement and quantum discord be shorter. It is found that quantum entanglement and quantum discord are similar in evolution.
In order to show the advantages of the super quantum discord with regard to the normal quantum discord, the super quantum discord and normal quantum discord in thermal equilibrium Heisenberg XYZ model with Dzyaloshinski-Moriya interaction were calculated and analyzed. The results show that the super quantum discord is always larger than the normal quantum discord and Dzyaloshinski-Moriya interaction plays a positive role to the super quantum discord. The super quantum discord is less affected by temperature than normal quantum discord. The stability of the quantum state can be improved by changing the ordinary quantum measurement with weak measurement.
In order to further enhance the global performance of evolutionary algorithms for solving minimum attribute reduction, a quantum-cloud-feedback-based attribute equilibrium dominance ensemble reduction algorithm (QCAEDER) with co-evolutionary elitists is proposed. First, an adaptive strategy of quantum revolving angle update operation based on cloud mode feedback is designed, so that the search space scope of quantum frog elitists can be adaptively controlled under the guidance of qualitative knowledge of cloud model and penalty factor feedback. Second, the attribute decomposition framework of co-evolutionary elitists with equilibrium dominance under the bounded rationality regions is constructed, in order to assist the quantum frog elitists necessary to attain the stable status of Nash equilibrium dominance by the average weighted credits. Third, the quantum frog elitists can extract attribute reduction subsets in the respective regions of equilibrium dominance by using the ensemble operation mechanism. Consequently, the global optimal solution of ensemble feature set can be achieved stably. The experimental results show that the proposed algorithm has achieved a higher performance on the efficiency, precision and stability of global optimal attribute reduction. Furthermore, the validation performed on brain MRIs electronic medical records of gestational age neonate demonstrates its strong advantage for real-world applications.
The transmission probability in graphene superlattices with triple periodic potential patterns induced by electric field was investigated by the transfer matrix method. It is demonstrated that the transmission probability as a function of incidence energy has more than one gap. The transmission gaps of electrons tunneling through a graphene superlattices can be modulated by changing the period number, incidence angle of electrons, height and width of the potential barrier. The transport properties in graphene superlattices with periodic potential patterns may lead to possible application in designing multi-channel electron wave filter.
Frequency doubling pulse laser around 532 nm was obtained through irradiating periodically poled lithium niobate (PPLN) crystal with a single mode laser beam, which emitting from a Yb-doped mode-locked fiber laser. Based on quasi-phase matching technology, the second harmonic generation (SHG) wavelength tuning can be realized by changing incident angle of fundamental wave that irradiates PPLN. Pumped by a mode-locked fiber laser which has a bandwidth of 60 nm, the pulse laser SHG was obtained from PPLN, and the output laser has a bandwidth of 1.5 nm and center wavelength of 532 nm. The SHG wavelength was continuously detuned by adjusting the angle of PPLN crystal. It worked out an angle tuning range of 0° to 25°, corresponding to the SHG wavelength tuning from 531.8 nm to 535.6 nm. The wavelength detuning is in good agreement with the theoretical analysis.
In the system of the aviation sensor, entrance of pitot tube used for speed measuerment is easily blocked and causes an accident. Currently the wind lidar is the unique solution to be a substitute for pitot tube. The common pulsed wind lidar cannot work in the near field due to blind spot at close range. In order to solve this problem, a monostatic coherent 1.55 μm continuous-wave (CW) laser Doppler wind velocimetry with an output power of 1 W was presented, in which a fiber-optics polarization-maintaining circulator, coupler and a balanced detector was used. A standarized experiment was carried out using a rotating platform, 5 m away from the telescope of the velocimetry. Results show that a velocity accuracy of 0.021 m/s and an excellent degree of speed correlation (R2=0.99) form a linear regression analysis of the system versus true rotating target. It was also showed that the speed of air away from telescope 25 m was implemented with the velocimetry.
The polarization spectral intensity modulation (PSIM) is an advanced polarization spectral measurement technology, and the measured data processing is the key link of PSIM to resolve the polorization spectrum information. The mathematics principle was presented on how all elements of Stokes vector spectrum of LUT are extracted from the measured data of PSIM system, starting from the modulation mechanism of PSIM technology, combined with relevant theory of digital signal processing (DSP), and the procedure of measured data processing for PSIM spectropolarimeter system was established. The spectropolarimeter experimental device based on PSIM was set up, and the measurement experiment was carried out, so that the light from the parallel light pipe directly and the polarized parallel light pipe output by polarizer were measured respectively. The measured data of the experimental device was processed according to the data processing procedure established previously to extract the spectropolarimetric information from it. The good consistency between the results of theoretical analysis and that of data processing verifies the method of data processing of spectropolarimeter based PSIM is correct.