The extra-cavity quasi-continue spiral phase modulation method for generating high peak power quasi- radially polarized beam was studied, which show that the generated beam is not perfect radially polarized, the radially polarized components determine the longitudinal electric field distribution, and the transversal field distribution is determined by both of the radially and the azimuthally polarized components. Considering the Richard-Wolf vector diffraction theory, the spatial and temporal distribution of the electric field vectors around the focal spot for various purities were simulated. The results show that the spatial and temporal distribution possesses the features of centrosymmetry and oscillation attenuation, and will be remarkably affected by the carrier envelope phase. Furthermore, the analysis indicates that the interactions between the focused pulse and the electron will be significantly determined by the spatial and temporalvector distribution at the focal spot. The results will provide valuable basis for the laser-particler interaction analysis and further polarization convertor designs.
Aiming at the problem of huge computation in pulsar period estimation methods, a direct pulsar period estimation algorithm was proposed. Based on the discussion of the influence of period errors on pulse time of arrival estimation methods, the mathematical model of the said period estimation method using TOA information is derived. In this method, a set of photon time of arrivals(TOAs) is divided into several segments in an equal time interval, and TOA information corresponding to each segment is calculated using time domain methods. According to the formula of the TOA information and period error, the Least Square method is adopted to estimate the period. A new intuitionistic criterion for the precision of pulsar period is developed by the value of the slope of the φ-t graph, which is different from the scheme that searches the perfect period based on maximum peak principle. Theoretical analysis and the results of experiments utilizing physical and numerical data are demonstrated that the presented pulsar period estimation method can achieve a precise and high-resolution period from a short observation of photon time of arrivals, which can help to realize the engineering application of X-ray pulsar navigation.
On the basis of the theory of indentation fracture mechanics, the relationship between the surface defect area and median crack of potassium dihydrogen phosphate crystals were analyzed theoretically. In the machine tool parameters and spindle speed in certain circumstances, the potassium dihydrogen phosphate crystal was processed by single point diamond turning under different cutting depth and feedrate. And then the ratio coefficient of unit area defect on the surface of the crystal was calculated. The experimental results show that the depth of surface defect is proportional to the ratio coefficient of area, which is consistent with the theoretical analysis, so the estimation method for the depth of surface defects by calculating the ratio coefficient of the surface defect area was processed. Finally, the high efficiency cutting process based on this method was proposed, the obtained arithmetic mean height value of surface roughness is better than that of 5 nm by the actual processing.
Liquid crystals are widely used in the display field because of their anisotropic optical properties. In order to study the modulation effect of the liquid crystal environment on the surface plasmon of metal nanostructures, this paper based on the finite difference time domain method, the extinction spectrum of gold nanocolumns in liquid crystal environment is analyzed, Computational space termination is provided by a combination of the perfectly matched layer absorbing boundary condition and periodic boundary conditions. Numerical simulation on the extinction spectrum characteristics of Au nanocolumns by the effects of different parameters, such as inclination angle, grating distance and periodic structure and so on. The results show that with the increase of the angle of the optical axis of the liquid crystal, the resonant wavelength appears redshift, and the modulation range is 40nm. The larger the grating distance, the weaker the interaction between the Au nanocolumns and the smaller of the resonant wavelength. With the increase of the cycle length, the secondary effect is more obvious. The surface plasmonics of the metal nanostructures can be adjusted by the optical properties of the liquid crystal. The results provide a theoretical basis for the study of the surface plasmon structure in the new photonic devices.
For the influence problem of the humidity on polarization transmission character under infrared wavebands, this paper applies Monte Carlo simulation for the common carbonaceous aerosol particles existing in nature. The influence of humidity on polarization transmission characteristics and polarization character difference under infrared wavelengths is researched. The results indicate that the Degree of Polarization (DOP), both linear and circular polarization, gradually rises with the increasing of humidity in the short wave bands; In the medium wave bands, the DOP of them descends with the increasing of the humidity; In long wave bands, the influence of relative humidity on DOP is minimal. To compare linear polarization with circular polarization, we demonstrate that the latter always performs better than the former in the short wave bands, whereas the former maintains its better polarization state. Therefore, in infrared polarization applications these conclusions introduce a method for the wavelength selection, humidity controlling and polarization state application.
Based on the coherent theory, the coherent properties of the new partially coherent beam were studied. The new partially coherent beam with the specific distribution of coherence was formed by the laser passing through a rotating special ground glass. The interference fringes produced by this beam passing through some double-holes with different hole spaces were experimentally recorded and their corresponding coherence degree was calculated. The coherence distributions of this beam under different propagation distances were experimentally investigated. The results show that, the coherence distributions of this beam are different with those of Gaussian Schell-model beams, and the degree of coherence increases with the increasing of propagation distances.
Using a pair of orthogonally linearly polarized beams as the light source, the azimuthally polarization axis finder, CCD cameras as image collector and Matlab software to process images, a polarization direction display system for polarized light was presented, which consisted of a He-Ne laser and an azimuthally polarization axis finder. The angle characteristics of this system were researched. The results show that the measurement accuracy is 0.480°, 0.168°, 0.528°, 0.421°and 0.340°, the measurement precision is 0.208°, 0.576°, 0.660°, 0.603° and 0.466° in the case that the polarizing angle of polarizer is 0°, 90°, 180°, 270° and 360°, respectively. By fitting a straight line to the experimental data, the linear correlation coefficient is 0.999 for this system. The elliptical polarization measurement system is constructed with a quarter-wave plate, analyzer and beam splitter with 50:50 splitting ratio. The measurement experiment of elliptically polarized light is completed, and the ellipticity of the elliptic curve is 0.198.
Aiming at the problem that the traditional line structured light plane calibration measurement accuracy is not high and the range of applications is small, a light knife plane calibration method of structured light system based on plane target was proposed. The iterative camera calibration was performed for target image without laser, and the light knife plane calibration was performed for laser target picture. The flat top laser detection center algorithm was proposed that made the light intensity coincide with the uniform distribution. The flat top laser was modeled as a rectangular step function, then the brightness of the background and foreground brightness were estimated to determine light stripe width, and then the light stripe centerge was obtained by calculating the center of gravity within the window of effective pixels. The algorithm was used to deal with pictures with different noise and different blocks, the results show that the root mean square errors are within 0.149 pixel and 0.176 pixel, respectively, which means that the algorithm has high anti-noise ability and high precision. The light strip center was extracted by using the proposed algorithm, the position of the light bar on the target was calculated. According to the light strip center 3D points of at least two postures, the light knife plane was fitted by least squares. By means of iterative camera calibration and knife plane calibration, 3D point cloud data was obtained in the stereo vision model by using triangulation. Two standard balls with mutual distance of 100.5mm were experimental measured, the distance between the camera and the standard balls is 500mm, the distance between two ball centers and the standard distance were compared, the measured average error is 0.236mm. It shows that the flat top laser detection center algorithm is practicable, and the method of light knife plane calibration basically meets the requirements.
A measurement method of signal-noise ratio for the single shot laser based on space scanning of optical Kerr gate was presented. In this method, the gate light and probe light transmit orthogonally in optical Kerr medium, the measurement of signal-noise ratio for the single shot laser was achieved by using an optical Kerr gate to make a space scanning for the probe light. With this approach, a single shot laser signal-noise ratio measurement was realized experimentally with a temporal window of 88.2 ps and a resolution of 2.7 ps. This method has no limitation on spectral range because of the gate is controlled by optical Kerr effect.
Sagnac effect can be enhanced with squeezed vacuum light input and Quantum Balanced Homodyne Detection (QBHD), which can result in the improvement of the gyroscope precision. By considering the phase sensitivity obtained by QBHD is related to the phase itself, the best sensitivity is achieved only at some certain value of phase. A scheme based photon counting was designed to extract the Sagnac output phase with Bayesian theory. The theoretical analysis results show that, the proposed scheme can break through the Shot Noise Limit(SNL), and the phase accuracy can reach Heisenberg Limit(HL) theoretically when the power of squeezed vacuum light and coherent light are equal. Meanwhile, the best phase sensitivity can be achieved at any value of phase, which is advantageous for gyro to reach the best sensitivity at any output phase.
To guarantee the high stability and high precision of an off-axis thee-mirror optical system space camera, a integration front frame structure was designed to support the second mirror and folded mirror according to the characteristics of the same height of second mirror and folded mirror in optical axis direction, and a topology optimization method based on constraint mode and free mode was proposed to optimize the front frame structure. Then, the integrated structure was assembled into the entire camera after optimization, and the finite element analysis of static was carried out. The results show that the camera maintains excellent static performance with the optical tilt between the primary mirror and secondary mirror being less than 9″ and the optical tilt between the primary mirror and fold mirror being less than 22.4″, the optical eccentricity between the primary mirror and secondary mirror being less than 0.021 mm, meeting the tolerance requirement of system. By free modal analysis and test to the integrated front frame structure, the results verify the correctness of the design method. The proposed topology optimization method can efficient avoid the defect of topology optimization based on constraint modal frequency that there is no relationship between the constraint points. It can provide reference for design the space camera with high-resolution and wide field.
A distributed intelligent control system was implemented to make streak cameras more protable and intelligent, which achieved the monitoring of working parameters, precise control of the electrode voltage and scanning patterns, additionally, image acquisition and processing. Based on the structure of Internet of things and client-server model, the system realized multimachine collaboration capabilities about wired and wireless devices extension and mobile monitoring. Furthermore, an adjustable self-protection high voltage ringing choke converter was designed for the system. The power supply realized the miniaturization by the simply self-excited topological structure, and its linear adjustment accuracy can reach 1%.The picosecond visible light streak camera with the intelligent control system was calibrated by the Nd:YLF pulse laser (Wavelength of 526.5 nmand pulse width of 8 ps).A dynamic spatial resolution of 20 lp/mm (CTF=14%), a dynamic range of 234:1 and a temporal resolution of 14 ps were reached.
Based on the structure of compounding zoom system, a mathematical model of three component continuous zoon design was proposed. Under the guidance of the model, a compact high zoom ratio continuous zoom optical was designed with medium-wave cooling 15μm, 640×512 staring focal plane array. The system works in the range of 3.7~4.8μm and F number is 4. By using this model to distribute the optical power, the initial focal point is calculated to obtain the focal length range of 9~740mm and the zoom ratio is 80×. The whole system used only two kinds of infrared materials of silicon and germanium and eight lenses were used. The system was U-folded by using the secondary imaging and two 45° reflecting mirrors, it effectively achieved 100% cold shield efficiency and controlled the horizontal and vertical dimension. It got the moving lens zoom track and cam curve of each group, and analyzed the continuous zoom optical system from MTF, spot diagram, distortion, narcissus, environment analysis and so on. The design results prove that the zoom system has the advantages of smooth zoom track, great narcissus controlled features and excellent image and it has also been found to apply to infrared imaging system matching with advanced middle wave detector greatly. Finally, the correctness and feasibility of the mathematical model are verified exactly.
The brightness uniformity and the crosstalk are the main factors which affect the applicability of the directional backlight lenticular-lens-based multiple autostereoscopic display. In this paper, by analyzing the causes of the generation of the crosstalk, according to the imaging optics principle of off-axis rays, the parameter calculating formula of the off-axis optical system which is consist of Liquid Crystal Display (LCD)panel column unit and cylindrical lens was derived. Then, a structure of butterfly-shaped LCD panel was proposed and used to design the module of the directional backlight autostereoscopic display. The simulation results show that, the directional backlight autostereoscopic 3D display backlight can eliminate the crosstalk. The crosstalk of the autostereoscopic display is less than 0.5% for the 90% viewing area of the view plane, the 10% peak width of the beam crosstalk area ratio is 0. The 90% peak width of the light beam is 1.37 times larger than that of the common liquid crystal cell structure, and the problem on the brightness of the image in different positions is improved.
An ultra-compact rectangular Mach-Zehnder (MZ) interference Electro-Optic (EO) modulator on InGaAsP/InP platform was proposed. This modulator consists of novel trench couplers and 90° waveguide bends. T type microstrip Travelling-Wave (TW) electrodes were designed for the L-shape waveguide phase shift arm of the MZ modulator. First of all, an upper bandwidth limit of this modulator was evaluated by using an equivalent circuit model of the TW electrodes. According to microwave characteristics such as impedance match, return loss and bandwidth, the transmission and input/output of electrodes and structure parameters of transition regions were optimized through a finite element analysis method. The simulation results show that being limited by the input of electrodes and transition regions, the overall TW electrodes exhibit an impedance match of >42Ω, return loss of <-15 dB and bandwidth of 65 GHz. Experimentally the return loss of -12 dB and the bandwidth of >20 GHz are obtained in terms of the fabricated Ti/Au electrodes on an InP substrate.
Aimed at the modulation technique used in indoor visible light communication systems, two power efficiency schemes named flip optical carrierless amplitude and phase modulation as well as unipolar optical carrierless amplitude and phase modulation are proposed in this paper. To ensure the signal be suitable for an intensity modulation/direct detection system, the first scheme forms the so called positive block and negative block based on the bipolar signal, the second utilizes a pair of samples including a zero level to mark signal polarity. Lambertian reflection model is introduced in visible light channel which is corrupted by additive white Gaussian noise. The theoretical bit error rate of the three modulation schemes involving DC biased optical carrierless amplitude and phase modulation over visible light transmission channel is derived. Meanwhile, the performance of bandwidth efficiency is analyzed and compared. Monte Carlo simulations is evaluated to corroborate the analysis. In addition, the effects of channel parameters on the system performance are discussed in this paper. The simulation results show that the bit error rate performances improve 6.9 dB and 29.9 dB when the radiation angle of LED is 0° compared with 30° and 45° in the room measuring 5 m×5 m×3 m. As the distance between the transmitter and receiver reduced from 2 m to 1 m, the optical carrierless amplitude and phase modulation system can obtain better performance of approximately 12 dB.
A Yb-doped mode-locked fiber laser with a tunable pulse width was built by using a cladding pumped all-PM(Polarization Maintaining) “figure-of-eight” cavity. The Dissipative Soliton Resonance(DSR) square pulses with a central wavelength of 1 064 nm, a repetition rate of 4.683 MHz, a tunable pulse width range from 0.8 ns to 5 ns and an average power range from 74.8 mW to 429.7 mW, are achieved. There is no polarization controller in the cavity. The mode locking state can be self-started only by adjusting the pump input, and then can be keep stable for a long time, and without lock-lose even under the condition of violent vibration. By using the two stage fiber amplifiers to amplify the power, the laser output with an average power of 100 W and the peak power as high as 26.68 kW is achieved.
To reduce the disturbance of acceleration effects on distributed feedback fiber laser hydrophone used in underwater sound detection, one symmetric structure with two diaphragms was designed and its anti-acceleration performance is investigated. The theoretical acceleration sensitivity model of the hydrophone with two diaphragms was established. After the relation between acceleration sensitivity and component size、materials parameters were analyzed, the structure of the hydrophone was optimized. Prototype of the hydrophone was fabricated and tested. The average pressure sensitivity reaches -132.6 dB with the fluctuation less than ±0.5 dB in the frequency range of 2.5~10 kHz, while the acceleration sensitivity is less than -28 dB. The results show that this structure of hydrophone ensures the high pressure sensitivity and flat response curve, whose anti-acceleration performance is improved at the same time, which will greatly enhance the signal-to-noise ratio of the hydrophone in the moving state.
A flat-response X-ray photocathode at the energy range of 0.1~5 keV was presented. The photocathode consists of two layers of metal material with same area and different thickness. After optimizing the thickness and microstructure of two metal layers, the proposed photocathode does not need complex corrections in the interested X-ray energy range of inertial confinement fusion experiment due to the flat-response characteristics. The flatness of the proposed X-ray photocathode with 4 kinds of materials respectively was simulated by adjusting the material, thickness and duty ratio. The simulation results show that the proposed photocathode has flat-response with flatness better than 5% at the X-ray energy range of 0.1~5 keV.
In order to design better optical structure of LED panel light and solve the existing direct-down LED panel light's shortcomings of large thickness and high light source density, this paper puts forward two mixed optical components including vertebral structure and half spherical structure that have both reflection and projectionand are applied to the design of ultra-thin direct-down LED panel light to increase the coupling distance of light to improve the light uniformity. The light uniformity and light efficiency are researched when two optical components with different structure are applied to LED panel light by Tracepro software, and further experiments were carried out by Taguchimethod. The results show that the light uniformity of the lamps with vertebral structure's components is 95.42% andits energy efficiency is 92.72% while the light uniformity of the lamps with half spherical structure's components is 97.67% and its energy efficiency is 92.65%, the reason why its light uniformity is higher than vertebral structure's is that the optical component with vertebral structure results in too concentrated light direction due to the directional reflection of the reflecting surface.
A tunable optoelectronic oscillator was proposed by utilizing optical injection-locking effect in a distributed feed-back laser diode. The optoelectronic oscillator loop mainly consists of an intensity modulator, a photodetector, an optical circulator, a distributed feed-back laser diode and a broad band radio frequency amplifier. In the proposed configuration, the distributed feed-back laser diode is key device. By utilizing injection locking of distributed feed-back laser diode rather than the commonly used radio-frequency band-pass filter, a high Q microwave filter is formed in optical domain, and short optoelectronic oscillator loop could be used in the proposed scheme. Thereby the effect of temperature sensitive of fiber on microwave signal stability can be declined and the system size can be reduced. Meanwhile, the central frequency of the microwave filter could be simply tuned and the tunability could be realized by tuning the wavelength and the injection power of the injection light. Theoretical analysis of the optoelectronic oscillator as well as the tunability of microwave filter was provided. Thus, experiment was done to verify the theoretical analysis. The results show that the proposed optoelectronic oscillator can produce the microwave signal with tunable range from 18.7 GHz to 21.6 GHz, and the measured phase noise at 1 kHz offset is -90 dBc/Hz.
Based on the double plane representation of the light field, aimed at the effect of light on the way of description influenced by coaxial translation, off-axis translation, coplanar rotation and off-planar rotation, and lens transformation between two reference plane of light field camera, this paper provided the corresponding matrix transformation equations. And using the transformation equations, the imaging model, sampling model, and radiation model of light field camera are established. Besides, on the view of light field coaxial space distance transformation, the digital refocusing process is deduced which can receive clearly imaging in any target scene point after got the imaging by focusing at a point. And moreover, by using the established model, the object is generated by computer simulation, and the model is used for digital refocusing on generation of features, the consistency of digital refocusing image and the directly focused images are verified.
In order to acquire color images of targets under Low Light Level(LLL) and improve the ability to distinguish targets from background at night, a color night vision image fusion method based on quadruple-band images was proposed.The quadruple-band filter with a transmittance at the center wavelength of three-band color lights and near-infrared band was designed by using Fabry-Perot(FP) filter, and the average transmittance is up to 90% at each transmission region. The quadruple-band filter was designed as a color-wheel filter structure,the spectral transmittance of each single band filter was measured by a spectrometer.The Signal Noise Ratio(SNR) of the night vision system after adding the filter was analyzed and calculated.The analysis results show that adding the filter will not introduce addition noise, and the SNR of the imaging system which added the blue, green, red and near-infrared band filters is equivalent to 19.59%, 38.45%, 47.28% and 46.70% to compare with that of the original monochromatic night vision system, respectively. Using a domestic Super Gen II image intensifier, quadruple-band image acquisition and color image fusion experiments were carried out in LLL laboratory, the experimental illumination is 1×10-1lx and 1×10-3lx, a set of images was adopted to conduct quality assessment. Experiment results show that, when the illumination is 1×10-3lx, the fusion color image is superior to the filtered blue and green monochromatic images both in gray mean, gray variance and information entropy, and the color image is enhanced by the use of the near infrared image, as a result the color image brightness is higher and the color identification is better.When the illumination is 1×10-1lx, the information entropy of the fusion color image is bigger than that of the red, green and blue color images. This research can give reference to the design and development of color night vision system.
In order to make full use of the abundant spectral and spatial information of hyperspectral images, a novel feature selection algorithm based on the structure preserving combination with the multi-scale spatial filtering and the hierarchical network is proposed. The feature subset that best preserving the global similarity and the local manifold structure is selected via l2,1 norm mathematical model. The bilateral filtering with multi-scale window and adaptive parameter setting is used for incorporating spatial information into spectral data automatically, enhancing the similarity within class and dissimilarity between different classes. The hierarchical network is introduced to achieve further integration of spatial and spectral information that benefit the classification. The influence of the hierarchical network depth and spatial filtering scale number is analyzed. The experiments validate the effectiveness of the algorithm. The overall classification accuracies reaches to 90.98% and 94.20% on Indian Pines and PaviaU data sets respectively, which significantly improve the classification of land cover compared with conventional methods.
The simulations of the noise distribution of vacuum state, single photon state and squeezed state in phase space were presented by Wigner function, respectively and the technology of the quantum lidar based on the squeezed field was systematically analyzed, including quantum coherent lidar and quantum lidar with squeezed light injection. Compared to the classical lidar, a higher squeezing degree benefits improvement of the detection Signal-To-Noise Ratio (SNR) for quantum coherent lidar, and a squeezing degree of 8dB would afford a 6.25-fold improvement in SNR theoretically, while the quantum lidar with squeezed vacuum injection has higher spatial resolution, which depends on the squeezing level of the squeezed vacuum and the gain of the phase sensitive amplifier. The results show that the quantum lidar has obvious advantages in the fields of weak signal detection and high-resolution imaging as the improvements of the signal-to-noise by using squeezed light.
In order to realize the single-qutrit state controlled bidirectional quantum teleportation, a protocol was proposed by using the methods of tensor representation and generalized three-dimensional Bell basis measurement. In this protocol, the quantum state of the controller Carol is arbitrary generalized three-dimensional Bell basis. The six-qutrit entangled state was chosen as the initial quantum channel, and the necessary conditions to judge whether any six-qutrit entangled state could be used as quantum channel were given. Based on the necessary conditions, with the aid of the unitary property of the SO(3) group element, a general method for constructing quantum channels was given by selecting its arbitrary two elements as the unitary matrices. Two specific examples were given, in which Alice, Bob and Carol worked together by performing generalized three-demensional Bell basis measurement and corresponding unitary transformation. At last, the exchange of quantum state between Alice and Bob was achieved, which verified the feasibility of the proposed protocol.