Gamma-Gamma model is a commonly used intensity scintillation model in wireless optical communications. For the problems of the complexity of the parameters models and the lack of reference for various approximate models, under Gaussian beam and using the method of simulation calculation, we analyze the effects of waveform condition, aperture dismeter, transmission distance, inner/outer scale, turbulent strength and wavelength on the characteristics of Gamma-Gamma model. The simulation results show that the effects of waveform condition, aperture diameter, transmission distance and turbulent strength cannot be ignored, while the effects of inner and outer scales, wavelength can be neglected. Moreover, as long as the ratio of aperture diameter to transmission distance remains unchanged, the Gamma-Gamma distribution characteristics will also keep unchanged. These conclusions provide reference and basis for the simplification of models in practical applications and the setting of system parameters for actual system.

Based on the non-Kolmogorov spectrum, using the extended Huygens-Fresnel principle, the analytical expressions for the spectrumof Gaussian-Schell model (GSM) beams propagating through non-Kolmogorov atmospheric turbulence are derived and used to study the influence of non-Kolmogorov atmospheric turbulence on spectral changes of GSM beams. It is shown that there exist spectral shifts (blueshift and redshift) and spectral transition of GSM beams propagating through non-Kolmogorov atmospheric turbulence. The spectral transition depends on the off-axis distance r, the general exponenta, the general structure constant [C2n], the inner scale l0, the outer scale L0, and the propagation distance z. With the increment of the general exponenta and the inner scale l0, as well as the decrement of the general structure constant [C2n], the spectral transition magnitude [Δ] will decrease and the critical position of spectral transition zc will increase. This work will provide theoretical model and computational basis for researches such as free space optical communications.

Resonance wavelength of long period fiber grating basically has a linear relation with the temperature changes, and the volatility of the wavelength corresponding to the loss peak can be represented by the standard deviation of the linear fitting. A new method for temperature sensing performance evaluation of long period fiber grating (LPFG) is proposed. The method is to use the ratio of the temperature sensitivity to the fitting standard deviation, P, to measure the sensing properties of LPFG. Lot of experimental results show that temperature sensitivity has a good consistence with the P value. The greater the P value is, the better the temperature sensing property of LPFG is, and the smaller the P value is, the poor the property is.

To accurately monitor the strain of surface of host materials, taking the surface fiber Bragg grating (FBG) sensor as an example, the relationship between the strain measured by the surface FBG sensor and the actual strain of the host material is deduced. The general expression of strain transfer coefficient of the surface FBG sensor is got. In experiment, the copper slice packaged FBG sensor by is adhered to the cylindrical sample surface and its strain transfer coefficient is got. The experimental result proves that the difference between strain transfer coefficients obtained in theory and in experiment is small and the theoretical derivation of the strain transfer coefficient is rational. The research results provide the theory guidance for the FBG sensor packaging and application.

In order to study the performance of frequency transfer based on fiber link, the impact of the transfer delay fluctuation upon the frequency transfer stability is analyzed. It is found that the transfer delay fluctuations caused by the variations in refractive index, the variation in fiber link length, and the excursion in laser output wavelength are major factors reducing the stability of frequency transfer. Using the newly established round-trip timing sequence model, it is shown that the transfer delay fluctuation resulting from temperature slow variation can be compensated, but the transfer delay fluctuation caused by temperature fast variation cannot be compensated. Reducing the rate of the dynamic junction temperature variations of laser is an effective method to improve the stability of frequency transfer. In order tosatisfy the requirement that the short term stability and long term stability are less than 10-15 s-1 and 10-20 d-1, respectively, some effective measure, must be taken and the rate of the dynamic junction temperature variations of laser must be precisely controlled to be less than 0.04 ℃/s.

The optical imaging and detecting system is important for noninvasive detection of latent fingerprints, in which the power utilization and intensity distribution uniformity of illuminating and exciting light source have great influences on the revealing effect and the detection ratio. Using the ultraviolet (UV) transmitting liquid core fiber as the optical guiding and transmitting element for the illuminating and exciting light source, the transmission characteristics of liquid core fiber in UV range are experimentally investigated. The transmission efficiency of 266 nm laser in the liquid core fiber and the relationship between the transmission efficiency and the fiber curve radius are obtained, and the intensity distribution of output beam transmitted in the liquid core fiber is measured with the uniform intensity distribution. Using the liquid core fiber as the optical guiding and transmitting element for the light source in the fingerprints optical detecting system can improve the light utilization and realize the uniform illumination condition equired, and the results have application values.

With the construction of a number of massive projects, the structure failure becomes more common and will probably lead to huge economic losses and casualties. It has important and practical significance to establish a complete set of structural health monitoring system for these massive projects. Damage detection is one of the core technologies for structural health identification. Although a variety of damage identification methods have been developed, accurately measuring the response of the structural information is still the premise of the effectiveness of damage identification. Damage in the massive structures cannot be predicted, so it is not advisable to perform health monitoring by means of strain gauges. We use quasi-distributed long-gage optical fiber Bragg grating (FBG), combined with the damage detection application in simply supported steel-concrete composite beam, to verify the performance of such a sensor. The test results show that damage identification efficiency is reduced with the increase in length of the quasi-distributed long-gage FBG strain sensor gage.

An improved phase generated carrier (PGC) demodulation algorithm is proposed to eliminate the effect of companion amplitude modulation in direct frequency modulation. The improved algorithm effectively eliminates the effect of companion amplitude modulation by using the third order harmonic component and the fundamental component. It reduces the generation of one mixing signal, cuts down the memory usage and the sampling frequency in the digital demodulation system. The Matlab simulation and CCS hardware emulation results verify the feasibility of the proposed algorithm.

Quantum-dot fiber has gradually become a research focus in optical communication field. This paper first introduces the development history of the CdSe/ZnS quantun-dot doped fiber. Whereafter, the preparation method of the CdSe/ZnS quantun-dot doped fiber with two kinds of different backgrounds is discussed. The spectral properties and peak gain of the photoluminescence are then comparatively analyzed. Finally, through the analysis we can get the proper background for CdSe/ZnS quantun-dot doped fiber. This research can give some useful experiences for developing other quantum-dot doped fiber.

Multi-spectral images of Phaseolus vulgaris leaves at the wavelength range of 400~720 nm with an interval of 5 nm are captured by using a multi-spectral imaging system which mainly consists of liquid crystal tunable filter (LCTF) and CMOS camera. Firstly，according to the principles of image brightness and band index, the value of band index and identifiability for Phaseolus vulgaris leaves are calculated respectively among every band. Then, through sorting the value of band index and identifiability for Phaseolus vulgaris leaves, it can be concluded that bands 545, 630, 645, 720, 650 and 570 nm have preferable identification with considering the characteristics of discrete gray levels and rich brightness of images and little correlation coefficient among different bands. Finally, the classification accuracy for Phaseolus vulgaris leaves is calculated according to the principles of minimum Euclidean distance and minimum spectral angle matching. The classification accuracy of characteristic bands for Phaseolus vulgaris leaves is 100.00% and 83.33% separately through using these two methods. We can draw a conclusion that these bands have ideal classification accuracy. Therefore, bands 545, 630, 645, 720, 650 and 570 nm can be used as feature bands for Phaseolus vulgaris leaves.

In order to study the effects of polarization state and effective numerical aperture on the focal full-width at half-maximum （FWHM） and evanescent depth in confocal total internal reflection Microscopy(CTIRM), according to the Richard-Wolf theory, the intensity distribution in the interface is calculated and discussed with linearly, circularly, radially and azimuthally polarized beams, respectively. Meanwhile, the numerical calculations of FWHM and depth are researched for three different effective numerical apertures (1.33~1.45, 1~1.45 and 1~1.12, respectively). The results indicate that the FWHM of radially polarized beam is 144 nm, breaking through the limitation of diffraction, which is also better than 330 nm of linearly and 360 nm of circularly polarized ones, by using 532 nm incident wave and 1.33~1.45 aperture. The sharper focuscan be got with the larger and thinner aperture. Also the smaller depth of transmission can be got with the larger difference of squares of upper and lower limits, for which 140 nm is the shallowest depth with 1~1.45 aperture. Compared to other polarizations, radially polarized beam is the most suitable choice for CTIRM. And by optimizing the effective numerical aperture, high horizontal resolutions and low axial fluorescent noise near the sample surfacecan be obtained simultaneously.

There are many factors that affect the measurement accuracy of the radius of curvature (ROC). So, high-precision measurement of the ROC has been one of the problems in optical measurement. In order to realize high-precision ROC measurement, a method to reduce the measurement error by environment compensation and improving alignment accuracy is presented. Firstly, the main factors that affect the measurement accuracy of the ROC are analyzed theoretically. And then a method for reducing the measurement errors in the measurement process and the corresponding compensation is proposed. Based on the theoretical analysis, typical convex and concave optical parts are measured respectively by interference method which is composed by a Fizeau interferometer and a high-precision displacement measurement interferometer in high-precision laboratory. Experimental results show that the measurement reproducibility is less than 0.2 mm and the relative errors of the measurement are 0.67×10-6 (2s) and 0.60×10-6 (2s) respectively through environment compensation and improving alignment accuracy. The high-precision ROC measurement is realized.

To accomplish the sub-aperture stitching testing for large aperture flat mirror under considerable adjustment error, we establish a reasonable stitching algorithm and mathematical model based on iterative gradient algorithm. At the same time, relative program is written for stitching. Combined with engineering examples, we measure a F800mm flat mirror with a F600mm interferometer in stitching method. In the measurement, we accomplish the alignment between sub-apertures with targets and the stitching result is smooth. Experimental results show that stitching measurements of large aperture flat mirror could be well down with the this algorithm under considerable adjustment errors.

Aiming at the characteristics and purpose of beam homogenization, existing evaluating methods for beam uniformity are analyzed, and their disadvantages are discussed. An assessment method combining uniformity and stationarity is introduced. The laser intensity distribution is obtained by CCD and the laser spot is analyzed by image processing. Then we quantitatively analyze the energy distribution and speckle of laser spot with uniformity and stationarity. The result indicates that the testing system fully satisfies the demand of laser spot assessment.

Since electrodes system is the key part of ArF excimer lasers, this paper is devoted to study the electrodes system of ArF excimer laser. By proper design of electrodes system, the optimized size of discharge zone is given and the approach of on-load voltage for cathode, anode and preionization electrodes is provided. Then a simplified configuration of electrodes system, consisting of cathode, anode, preionization electrodes, ceramic materials and working gases, is obtained. The electric field under different on-load voltages is calculated based on the simplified configuration of electrodes system. Simulation results show that electric field of discharge region is symmetrical, and the design of electrodes system is reasonable.

The optical fiber transmission model, i.e., the nonlinear Schrodinger equation, is solved by split-step Fourier algorithm to research the effects of fiber-optical dispersion and nonlinearity on a new closed-loop dual-directionally chaotic secure communication system with three lasers. The effects of the actions of dispersion, nonlinearing, and combination action of dispersion and nonlinearity on the chaotic signal and the demodulated message quality are analyzed as the optical fiber transmission distance increases. The results show that: the dispersion leads to the broadening of chaotic signal, and the increase of broadening ratio, and reduces the synchronization performance of chaotic signal with the optical fiber transmission distance increasing, which results in the degradation of the demodulated message quality. Nonlinearity does not affect the time-domain waveform of chaotic signals, but the combination effects with dispersion make the chaotic signal change rapidly, as a result, the synchronization performance of chaotic signals varies rapidly, and the demodulated message quality sharply deteriorates.

The method of chaotic controlling is presented via controlling the phase in He-Ne lasers under optical feedback, which is based on the analysis of the chaotic dynamics characteristics of He-Ne lasers in the feedback light. The dynamics equations and physical model under the control of laser chaotic feedback phase cycle are established. Selecting appropriate feedback coefficient, the laser chaos can be controlled to a steady state, periodic state, and chaos state by controlling the feedback coefficient and the phase-shift of the feedback light using the phase controller in the feedback channel. Under the conditions of different intensities of feedback light, it is shown that, after a certain time of relaxation, chaos can be controlled into periodic state, dual periodic state, triple periodic state and multiple periodic state respectively by 1/8, 1/4, 1/2 and one wavelength periodic phase-shift modulation.

To discover how laser shock processing (LSP) affects the fatigue property of the blade made of K4030 alloy, the samples cut from blades and blades made of K4030 are laser shock processed , then the microstructure, micro-hardness, residual compressive stress and surface roughness of the samples are tested, and the fatigue life of the blades as well. The test results show that no obvious change of the surface roughness is found；a residual compressive stress more than 450MPa is developed in a depth of 1mm from the surface; some grains are observed refined in the grain boundary of shock region；the micro-hardness improves in a depth of 0.8mm from the surface， and the surface micro-hardness improves 16%. Fatigue test result shows the life of blade made of K4030 alloy is improved visibly after it is laser shock processed. So it is feasible to improve the fatigue life of K4030 blade using laser shock processing.

Intra-channel nonlinear effects in quasi-linear strongly dispersion-managed transmission are analyzed in detail by numerically solving the multi-pulse coupled modified nonlinear Schrodinger equations. The influences on transmission of intra-channel four-wave mixing (IFWM), intra-channel cross-phase modulation (IXPM), and self-phase modulation (SPM) are compared for different bit patterns, different transmitted powers, and different bit rates. Results show that, in the case of higher bit rate, IFWM is the most important nonlinearity while SPM plays a negligible role as compared to IFWM or IXPM. As the bit rate decreases, both IFWM and IXPM decline while SPM relatively increases. For a fixed bit rate, all of the three nonlinearities increase with the imcrease in input power while IFWM has the fastest increasing rate and SPM the lowest one. We propose to apply a large pre-broadening to the input pulses for quasi-linear strongly dispersion-managed transmission and find that it can efficiently suppress intra-channel nonlinear effects such as IFWM, IXPM and SPM.

A 10× mid-wavelength infrared (MWIR) continuous zoom optical system is designed for cooled 320 pixel×240 pixel staring focal plane array detector. The system uses mechanical positive compensation zoom system. 100% cold stop efficiency is realized by secondary imaging system. Two common infrared optical materials, i.e., silicon and germanium, are used. By introducing reasonable aspheric and diffractive surfaces, the aberrations are balanced. By using ZEMAX optical design software, the system is optimized for continuous zoom is the range of 20~200 mm. After design and optimization, the system only uses 7 lenses to realize 10× continuous zoom. The F number is 2, the working wavelength is 3.7~4.8 mm, the modulation transfer function (MTF) at spatial frequency of 16 lp/mm is larger than 0.4, and the root mean square (RMS) radius is smaller than 16 mm. It has a resolution close to diffraction limit and satisfies the requirement of imaging. Moreover, the system has a smooth curve zoom and meets the zoom requirement.

The 1300 megapixel mobile phone camera lens which is composed of five plastic aspheric lenses and an infrared (IR) filter is designed. We use a 1/3 inch (1 inch=2.54 cm) CMOS as the image sensor, and the pixel size is 1.12 mm. The mobile phone lens has an effect focal length of 3.9 mm, an F-number of 2.2, and a field-of-view (FOV) of 78°. All modulation transfer function values at the half limiting frequency are greater than 0.4. Simulation results show that the lens has an excellent imaging performance. The maximal distortion of the lens is less than 2%, the relative illumination is more than 36%, and the tolerance is rather loose. It can satisfy the requirements of practical production.

When measuring the laser beam quality of different wavelengths, in order to avoid the calibration of focal plane position and reduce the measurement error, the superachromatic lens is researched and designed covering the ultraviolet to the near infrared band. Based on the theory of wave aberration, the equations for the initial structure of the superachromatic lens are derived. The superachromatic lens of wide spectral range is designed by the optical design software Zemax. Its waveband is 350~1100 nm, the focal length is 200 mm and the entrance pupil diameter is 25 mm. The structure of optical system, longitudinal aberration, focal shift curve and modulation transfer function (MTF) are given. Design results show that the spherical aberration curves of different wavelengths at 0.707 aperture intersect at one point approximately, achieving the superachromatism; the focal shift in the working waveband is only 26.3 [μm], and the focal plane position is fixed basically; the MTF is close to the diffraction limit in the range of cutoff frequency, meeting the measurement requirement of laser beam quality from ultraviolet to near infrared.

To meet the requirement on solar simulator irradiance uniformity，we put forward a design method to optimize the integrator and condenser. A great improvement in irradiation uniformity is achieved while maintaining a high energy efficiency. Simulation is performed by optical software LightTools to test and verify the correctness. By comparing characteristics of homogeneity with the original optical system design of the solar simulator, the correctness and feasibility of the optimization method adopted are proved.

Due to the zero phase variation and impedance matching to free space, zero-index material is used to control the electromagnetic radiation patterns. We design a new type collimator and optical splitter structure based on near-zero-index material. Such structures can implement the beam transformation from cylindrical wave to parallel wave and optical splitting. The numbers of the splitting beams,the width and the direction of the beams can be correctly tailored. All the simulation results show that our designs have perfect performance.

The effect of barrier layer periodicity asymmetry on photonic crystal quantum well transmission spectrum is studied by transfer matrix method. The results show that when the periodicity asymmetry is 0, transmission peaks become sharper as the barrier layer periodicity increases, but the transmittance is constantly equal to 100%. When the barrier layer periodicity asymmetry is any nonzero constant，the transmittance is below 100%; while with the increase of barrier layer periodicity, the transmission peaks sharpen with a constant transmittance. The transmittance of transmission peaks decreases with the barrier layer periodicity asymmetry increasing, and the greater asymmetry is, the faster the transmittance decreases, and the faster the transmission peaks narrow. These properties can provide theoretical basis for construction, preparation and design of the photonic crystal model.

Characterization of femtosecond pulses is an important technology inthe femtosecond laser research field. We introduce the current research status and recent progress of a new method named self-referenced spectral interferometry (SRSI) whichis a simple and high-performance method. The advantages and disadvantages of three different SRSI methods by using three third-order optical nonlinear processes (cross-polarization wave generation, self-diffraction and transient grating) are compared in detail. The comparison will provide a comprehensive reference forthe related research and application in the near future.

The complex photoelectric environment on the battlefield is very important for laser identification friend or foe (IFF) system. The laser threat signal, combat situation and laser detection approach are analyzed. The complex laser threat signal environment of laser IFF system on the battlefield is researched. Taking the case of armoured vehicle as laser IFF system installation platform as an example, test conditions construction of complex photoelectric environment is analyzed, and the adaptability test method is discussed.

Rare-earth doped fibers are the foundation of fiber lasers while the photodarkening of doped fibers is a significant factor which is harmful to the stability of laser output power. In this paper, we review the mechanics of photodarkening, and the influence of photodarkening on the fiber lasers, as well as all kinds of methods which can mitigate the photodarkening effects in the doped fiber, with the aim of providing useful information for the related research.

Microfluidic optical waveguide devices are novel optical components based on turning microfluidic, which have wide potential applications in biomedical and environment monitoring and so on. We describe the element structures and present the operation principles of microfluidic optical waveguide devices. The recent developments in the area of the microfluidic waveguide devices are reviewed, and the research tendency in near future is predicted.

A novel approach for analyzing spatiotemporal couplings in ultrashort pulses is presented using amplitude correlation functions. Amplitude correlation degrees and correlation bandwidth are defined, which can readily indicate the severity of spatiotemporal couplings. Intuitive pictures of pulses with different amounts of spatial chirp are given. With amplitude correlation functions, the amplitude couplings in ultrashort pulses, such as the first-order spatial chirp and angular dispersion caused by angular dispersion elements and the second-order spatial chirp caused by diffraction effects, are studied, and corresponding analytical expressions for the amplitude correlation degrees are given. It can be found that the refraction and diffraction of broadband optical pulses are frequency dependent, resulting in the decrease of amplitude correlation degree and leading to a coupling of spatial and temporal effects. Specifically the severity of the spatial chirp caused by an angular disperser increases with the increase of propagation distance and finally tends to be constant. Moreover, as the diffraction of ultrashort pulsed Gaussian beams is frequency dependent, the second-order spatial chirp of ultrashort pulsed Gaussian beams caused by diffraction effects will decrease during propagation. Finally, the severity of angular dispersion caused by an angular disperser does not vary as the beam propagates in the free space.网络出版日期: 2013-12-11