The power spectral density was investigated to analyze the seeing-limited performance of large telescope. The Karman spectral with different frequency knees and the Power Spectral Density(PSD) slope were used to simulate the atmosphere turbulence. And the Zernike polynomials was used to analyze the low order deviations. Combining the two kinds of deviation, the numeral modal was built to simulate the system. Lastly, by analyzing the PSD of actual sample and the sample combined with the numeral atmosphere turbulence, the separation of the abberations with different sourse was obtained. The results show that the proposed method can specify the performance of the large telescope under limited seeing.

According to the Lambert-Beer law,we derived mathematical model to measure the target gas concentration,and deduced the function which could be used for characterizing the relationship of the output voltage of the two detectors and the target gas concentration.The aim of calibration process is to determine the values of those two constants which depend on the length of the chamber,the gas absorption coefficient and the detector voltage detectivity in the above expression.Secondly,according to the feature of the measurements’ zero point changes with current temperature,the relationship between zero point and temperature was formulated.It can be used for zero temperature compensation and correlation of coefficient calculation.The scale temperature compensation method is the way to revise the function expression of the output voltage of the two detectors and the target gas concentration by introducing scale temperature compensation factor.The corrected function expression is used for compensating scale temperature and calculating the compensation coefficient of scale temperature compensation.Finally,the calibration and temperature compensation method above was applied to coal mine non-dispersive infrared methane transducer and the test results of standard gas samples testing under various ambient temperatures conform to the requirements in infrared methane sensor standard.

To realize the non-contact temperature monitoring of high voltage electrical equipment, a non-contact (0-1.5 m) fluorescence fiber temperature measurement system was designed. Using the relation between fluorescence and temperature of rare earth materials, temperature measurement was achieved by measuring the excited fluorescence lifetime of the fluorescent material which was attached on the object. The analysis indicates that the received light energy can be increased through adding a converging lens and a converging cone. In the experiment, the fluorescence intensity curve was obtained, and the temperature was aquired according to the relation of fluorescence lifetime and the temperature of the measured object. The measurement error is less than 1 ℃, ensuring its application in high-voltage environment.

The working principles of Interferometric Rayleigh scattering velocimetry using a Fabry-perot interferometer is presented. An interferometric Rayleigh scattering velocimetry apparatus consisted of a high resolution F-P interferometer, an injection-seeded Nd∶YAG laser and an intensified CCD was developed. In theory, the measurement uncertainty of velocity is 10 m/s, the recommendations for system improvements were given. Non-intrusive measurement of velocity in unseeded gas flow is performed to demonstrate this technique, flow velocity of 366 m/s was obtained in a supersonic free air jet flow.

Considering that the switching speed of the Y-fed coupler Electro-Optic (EO) switch with two-section seperated reversed lumped electrodes is slow,through push-pull poling on the wavegides in the two EO regions,a bias-free high-speed travelling-wave line EO switch was designed.Design and optimization were performed on electrode parameters for obtaining low driving voltage,good impedance match and less-mismatch between optical index and microwave index.Besides,by using Fourier transformation on the applied square-wave switching signal,a novel analytical technique was presented to model and characterize the switching response.Numerical calculation results of the optimized device indicate that,under 1 550 nm central operation wavelength,the 3 dB state voltage is 0 V,and the upper-and lower-branch state voltages are -1.34 V and +1.34 V,respectively,indicating a switching voltage of 2.68 V.The insertion loss and crosstalk are less than 3.55 and -30 dB,respectively,and the 10%-90% rise time and fall time are both about 3.90 ps,indicating a cutoff switching frequency up to 128.2 GHz.The proposed high-speed device structre and numerical technique are of well meaning for the design and performance evaluation of a similar device based on Y-fed coupler structure.

The asymmetric Fano-resonance spectra was proposed to obtain a larger sharpness and elevate the sensitivity of ring resonator, the Eye-like resonator is utilized to generate the asymmetric Fano-resonance spectra, the Eye-like resonator consists two rings resonators with the outer loop coupled to two bus waveguides and the inner loop couple to the outer loop. Numerical calculation of spectra on the drop port was utilized by the transfer matrix method, as the round trip loss varies, the value of sharpness increases with the round trip loss;by changing the outer loop coupling coefficients and inner loop coupling coefficients, the maximum value of sharpness of Fano-resonance change slowly;as the round trip loss varies and a lager range of the outer loop and inner loop coupling coefficients, the corresponding transmission at the resonant point remains almost unchanged, about －6 dB. The sharpness of Fano resonant peak is insensitive for the coupling coefficients, which can reduce the requirements of manufacture of coupling region.

The scattering of an arbitrarily incident Bessel beam by complex particles with inclusions was investigated by utilizing the method of moments and its fast algorithm based on surface integral equations. The mathematical description of the electromagnetic field components of the arbitrarily incident Bessel beams were derived by using the vector expressions of zero-order Bessel beam in combination with rotation Euler angles. Based on equivalence principle, the surface integral equations were established, which could solve the scattering problems involving complex particles with inclusions of arbitrary shape and structure. The scattering of an arbitrarily incident Bessel beam by several selected particles with inclusions was simulated. The numerical results indicate that the Differential Scattering Cross Section (DSCS) for a Bessel beam is smaller than that for a plane wave and increases with the decreasing of the half-cone angle. Moreover, the position offset of the beam center decreases the DSCS, and the DSCS will be quite sensitive to the incident angles. The obtained results are expected to provide useful help for techniques of laser detection on particle, diagnosis, and manipulation.

In order to select the suitable modulation parameters for harmonic signal and meet the different measurement requirements,taking a oxygen monitoring system with 760.77 nm absorption wavelength for example,the impact of different amplitude values on the symmetry,both sides minimum interval and signal integrity were discussed by changing the sawtooth and sine signal frequency.The result show that the Sinmulink values are highly relevant with experiment values and a good second harmonic signal is obtained when the ratio fsin/fsaw is 1 000.The results have profound guiding significance for the system precision,stability,repeatability and other important aspects of the experimental system.

In order to improve the output spectral characteristics of 980 nm semiconductor laser, the expression of transmittivity of dual fiber Bragg grating was deduced by the transfer matrix theory. The influence of fiber Bragg grating length and cavity length on output spectrum was conducted by simulation, the result shows that the fiber Bragg grating length′s influence on output spectrum is greater than fiber Bragg grating cavity length′s, and the width of output spectrum can be reduced by lengthening the fiber Bragg grating length. The dual fiber Bragg grating was fabricated on the tail fiber of 980 nm semiconductor laser to reduce the output spectral width of laser and to improve the stability of the laser output spectrum. The experimental results show that the center wavelength of 980 nm semiconductor laser changes only 0.06 nm when the environment temperature changes within the range of 0℃ to 75℃.

The wavefront aberrations of human eye are nor static but fluctuate over time which can cause dynamic changes in both the optical properties and the visual performance of human eyes. The dynamic wavefront aberrations across pupil diameter of 3 mm and 6 mm for 10 eyes with cliopter of 0 D-－5.0 D were measured at temporal frequency of 25 Hz by the modified Hartmann-Shack sensor. Each human eye was tested 125 times in a duration of 5 s. To ensure that measurement did not introduce artifacts, the dynamic wavefront aberrations of 3 mm and 6mm for an artificial eye was acquired. The average amplitude of the fluctuation of the total rms wavefront error of 3mm and 6 mm for 10 eyes is 0.08 μm and 0.105 μm, respectively, which is greater than Marechal diffraction tolerance. The amplitude of the fluctuation of rms wavefront error from 3rd up to 7th order decreases monotonically as the Zernike order increases, the amplitude of the fluctuation are 0.06-0.02 μm. The frequency of the fluctuation for all the Zernike order is 6 Hz.

The energy transfer between a subunit of Fenna-Matthews-Olson antenna complex of green sulfur bacteria and its reaction center (sink) was investigated. Through fixing the site energies of bacteriochlorophyll molecules and the coupling strength between the Bacteriochlorophylls(BChls), a Hamiltonian of the Fenna-Matthews-Olson-sink and its reduced models were constructed. Based on the Hamiltonian, the evolutions of the populations of different BChls and the sink states was investigated by a hierarchical equation of motion approach. In order to observe the coherence between different states in the processes of energy transfer, the two-dimensional third-order photon echo spectra of the Fenna-Matthews-Olson and its reduced models in different waiting times were calculated. The results imply that for energy harvesting there are some redundant chromophores in the Fenna-Matthews-Olson complex.

Two novel carbazole-benzothiazole derivatives 3-((2-benzothiazole-2-yl) ethenyl)-N-ethyl-carbazole and 3, 6-bis ((2-benzothiazole-2-yl) ethenyl)-N-ethyl-carbazole containing carbazole as a donor and benzothiazole as an acceptor were synthesized and characterized by 1H-NMR spectra and UV-Visible spectrophotometer. The compound-doped polyimide thin film with mass fraction 4% were prepared by doctor blading on the glass substrate. The linear and nonlinear optical properties of the thin film were studied using the transmission spectrum method and Z-scan technique with 30 ps pulses at 1 064 nm, respectively. The values of the nonlinear absorption coefficient and nonlinear refractive index of the two thin films were β1=－2.118 9×10－10 cm/W, r1=2.285 2×10－14 cm2/W, β2=－1.275 6×10－9 cm/W, r2=－7.039 9×10－14 cm2/W, respectively. The Z-scan results revealed that the first compound-doped polyimide thin film exhibited reverse saturable absorption and self-focusing effect while the second compound-doped polyimide thin film exhibited reverse saturable absorption and self-defocusing effect.

For the problem of information crosstalk that caused by periodic soliton string collision in the transmission,the modified symmetric split-step Fourier method that approximated by higher-precision Simpson algorithm was presented,and then the soliton string characteristics and transmitting procedure were simulated.It is impoint that the precision of method is more over than two orders of magnitude compared with the traditional method.The experimental results show that the solitons collision was decreased and the collision-free dependent transmission distance was increased,for the soliton pairs,three-soliton,four-soliton,five-soliton and six-soliton when only considered the self-steepening coefficient were 0.02 and only considered the self-frequency shift coefficient were 1,1,3,2 and 1.5,respectively.Meanwhile,the self-steepening and the self-frequency shift effect were simultaneously considered,the self-frequency shift effect was predominant effect.The results indicated that the suitable parameters have a significant influence for the amount of information of soliton transmission.

A light optical system with wide bands, large field of view and lightweight was designed. The focal length is 35 mm, F-number is 7.5, working wavelength range is 400-900 nm, and a view angle is 60°. A complex double-Gauss construction was applied in the designed system, and spherical surfaces were used in all lens, so that the total length could be 115 mm and minimum modulation transfer function could be greater than 0.45 at 70 lp/mm. Barrel distortion and aberration vignetting were used to improve illuminance distribution homogeneity, marking the margin field illuminance reach 80% and the image plane illumination uniformity be 8%. This optical system has a good thermo-optical properties, can achieve fine image quality at the working temperature range of 0-40 Celsius, which is suitable for the deep space exploration.

Aim at the lacks of uniformity for large view angle illumination in the near-field and low efficiency of single freeform-surface lens of LED, based on the edge-ray theory and grid partition method, a double freeform-lens with large view angle of LED was designed, the inner surface was elliptic and the outer surface was freeform. The incident rays of LED diverge from the inner surface of the lens, and the direction of the emergent rays were controlled by the outer surface, which realized large view angle uniform illumination and reduces losses of total reflection, thus, improving the luminous efficiency. The extended source ray-file was employed to do optical simulation for the lens model, the feedback optimization method was used to optimize the outer surface and improve uniformity of near-field illumination. The results show that under the condition of same near-field distance, with the beam angles at 143°and 151.8°, respectively, the corresponding illumination uniformity values of single freeform-surface lens are 0.55 and 0.40, and the efficiency values are 92.0% and 80%.While the proposed double freeform-surface lens greatly improve illumination effects, with 0.84 and 0.85 illumination uniformity and 98.8% and 95.0% efficiency.

A novel octagonal duel-core photonic crystal fiber based on tellurite glass was proposed.Using the Full-vector finite Element Method (FEM) and coupled-mode theory,impacts of structural parameters on characteristics of the coupling was analyzed.The results show that the coupling length decreases significantly as the value of hole-pitch decreases,but the relative coupling length changes slightly as the value of hole-pitch decreases;the coupling length increases slightly as the value of air hole diameter increases,the relative coupling length increases significantly as the value of air hole diameter increases;the coupling length increases slightly as the value of ellipticity increases,the relative coupling length increases significantly as the value of ellipticity increases.The performance of the design polarization splitters was desired when the relative coupling length is 1.Then a kind of polarization splitters based on the proposed dual-core PCF was obtained.The two polarized lights are separated entirely with 139 μm fiber,simultaneously the polarized light extinction ratio is -53.46 dB at the wavelength of 1.55 μm.Besides,the bandwidth is over 120 nm when the extinction ratio is less than -20 dB,which exhibited high performance of splitting one light into two orthogonal polarization states comparing to the other duel-core polarization splitter with highly extinction ratio and short length.

Through the analysis of the intensity ratio of anti-stokes and stokes light of the backscattering light,a multimode optical fiber Raman temperature sensing system had been developed based on Raman scattering and optical time domain reflection principle.Using a new type of dynamic temperature calibration program for fitting low and high temperature zone respectively,which improved the measuring-temperature accuracy up to ±1 ℃.This paper respectively conducted the system temperature resolution,temperature measurement precision,spatial resolution and repeatability experimental verification.The experimental results show that the temperature resolution of 1 ℃,the spatial resolution of 1m,the system stability is good and can adapt to the complex environmental change.

The pilot-aided method was adopted for estimation and compensation of sampling clock frequency offset in CO-OFDM systems to improve the system′s performance .And the pilot arrangements were simulated and discussed by comparing with five different location of pilots inserted,the optimal location of pilot inserted was obtained.The simulated results show that the method can work quite effectively even with large sampling clock frequency offsets,and the loss of optical signal-to-noise ratio is less than 1 dB.Therefore,it can reduce the cost of system;the location of pilots will impact the performance of the algorithm,the average insertion of pilots is optimal.With increasing sampling frequency offset,if the method can not work well,the pilots should be inserted at the low frequency sub-carriers.

In monitoring intrusion incidents based on phase-sensitive Optical Time Domain Reflectrometer(φ-OTDR), the methods of combining elements, which are the past records of a single point, the data of neighboring points, and the ratios of peak values, were introduced. The advantages and disadvantages of those methods by accuracy of identification, time consumption, complexity and stability were measured. The experimental results demonstrate the method combining the past records of a single point, and the data of neighboring points achieve the best performance, the identification accuracy rate can be as high as 100%, this method has a good adaptation in different frequencies. The research will contribute to the signal processing part of applying φ-OTDR to security system.

The demodulation speed has become the key issue limiting the application of fiber optic Fabry-Perot nonscanning correlation demodulator.A fast fiber-optic Fabry-Perot (F-P) nonscanning correlation demodulator based on Super Luminescent Diode(SLD) was proposed,its principle and signal characteristics were analyzed.To improve the signal stability,envelope detection based on wavelet was presented.Theoretical calculations show that the error of the result is only 0.33% with this algorithm,while the error is 4.33% without it.A experimental prototype was made and tested,when the demodulation speed is 1.5 KHz,the demodulation erorr is only 5 nm with this algorithm.The experimental results indicate that envelope detection based on wavelet can improve the demodulation stability and accuracy of the fast fiber optic Fabry-Perot nonscanning correlation demodulation system,providing a stable and efficient algorithm for the fast fiber optic Fabry-Perot nonscanning correlation demodulation system.

With finite element method,a hexagon High Birefringence Photonic Crystal Fiber (HB-PCF) with two zero-dispersion dots and CdSe/ZnS quantum dots film was designed.The dispersion and loss characteristics of the designed HB-PCFs with the different thickness of CdSe/ZnS quantum dots films were analyzed.The results show that HB-PCFs with CdSe/ZnS quantum dots films exist the fundamental modes along the x- and y-axes of fibers.As pump wavelength increases,the birefringence of HB-PCFs with the same thickness of CdSe/ZnS quantum dots films increases gradually.And their dispersions increase first and then decrease along the x- and y-axes of fiber.The losses of HB-PCFs are close to zero in the visible region while they increase gradually in the infrared region.For the different thickness of CdSe/ZnS quantum dots films,the birefringence of HB-PCFs decreases gradually with the increase of quantum dot film thickness for the same pump wavelength.Their dispersions decrease gradually along the x- and y-axes of fiber,and their two zero-dispersion dots are close to each other,and their losses increase gradually.These research results indicate that the dispersions and losses of the HB-PCFs can be controlled effectively in experiment by depositing the different thickness of CdSe/ZnS quantum dots films and choosing a suitable pump wavelength.

Within the framework of the effective-mass approximation, the binding energy, optical transition energy, oscillator strength, and radiative lifetime of ionized donor bound exciton (D+X) in a Quantum Dot (QD) were calculated, assumed that the ionized donor was located at the disk axis, the disk-shaped QD consisted of a finite length cylinder of ZnO material surrounded by MgxZn1－xO. The calculations were performed by using a suitable variational wave function for finite confinement potential at all surfaces, including the strong built-in electric field effect due to the spontaneous and piezoelectric polarizations. Calculated results reveal that the disk structural parameters (height and Mg composition in the barrier) and the donor position have a strong influence on the binding energy, optical transition energy, oscillator strength, and radiative lifetime of (D+X) complex. As the disk height increases, the binding energy, optical transition energy, and oscillator strength both decrease, whereas the radiative lifetime increases. The influences of disk height on the binding energy, optical transition energy, oscillator strength, and radiative lifetime become more prominent for the QDs with higher Mg composition. The binding energy (the optical transition energy) has a maximum (minimum) when the donor is located in the vicinity of the left interface of the QDs. On the contrary, the binding energy (the optical transition energy) has a minimum (maximum) when the donor is located in the vicinity of the right interface of the QDs.

Vapor Etching (VE) was used to etch diamond wire sawn mc-silicon wafers. The vapor was generated from heating the acid mixture solution of HF-HNO3 in the volume ratio of 1: 3 (the total volume of the solution is 400 mL) at 90 ℃. The results showed that etching for 15 minutes, saw marks can be removed and lots of small corrosion pits which appeared in big corrosion pits were densely covered with silicon wafer surface, the average size of the corrosion pits was about 1 μ m, while that by wet acid etch was over 10 μ m. The wafer surface roughness with VE method is actually 3 times higher than that with traditional wet acid etching method. The effect of VE is obvious and the reflectivity is low to 12.11%.

In order to obtain the influence of two temperature-dependent energy transfers (the one Energy Transfers (ET) from band edge to defect states in one nanocrystal and the other energy transfers from different size nanocrystals) on fluorescence emission intensity of CdTe nanocrystals, the fluorescence emission spectra of CdTe nanocrystals films at temperature from 78 to 300 K were investigated. The results of the experiment show that the fluorescence emission spectra of CdTe nanocrystals films exhibit band edge emission centered at about 520 nm and defect fluorescence emission centered at about 605 nm, and the fluorescence intensity presents different change regularity with temperature increasing. At the first stage of temperature(78～140 K), for the green-emitted CdTe NCs, large size ones have fewer defect sites and the fluorescence emission efficiency is higher than the small size ones. The energy transfers from small size ones to large, resulting in increasing of the band edge fluorescence emission intensity. At the second temperature stage(140～300 K), the defect and band edge fluorescence emission intensity gradually decreases. Therefore, the ET rates with temperature are prominent at the first stage of temperature and subordinate at the second temperature stage, compared to the nonradiative recombination rates. To further prove the influence of ET on the fluorescence emission intensity, the CdTe NC films were dried under vacuum conditions, which could avoided the atmospheric oxidation and therefore had fewer defects on the NCs surface. CdTe NCs were put in PEG matrix film in order to reduce the ET rates from different size nanocrystals . Fluorescence emission intensities of as-prepared CdTe NC films were decreased with temperature at the first stage and coincided with the variations of ET rates with temperature.

The oxyfluoride tellurite glasses doped with Dy3+ions, Tb3+ ions respectively and co-doped with Dy3+ ions and Tb3+ ions were synthesized by high-temperature melting method. Densities of different molar concentrations of Dy3+ions and Tb3+ ions were measured. Transmission spectra, excitation spectra, emission spectra and decay time were investigated. And the energy transfer between Dy3+ ions and Tb3+ ions were studied. The results showe that all the glass samples have a high density with more than 5 g·cm－3, and up to 6.09 g·cm－3. Dy3+ ions can effectively sensitize the luminescence of Tb3+ ions, when molar concentrations of Dy3+ ions is more than a certain concentration, the emission intensity of Tb3+ ions will be decreased because of the concentration quenching effect. With 1mol% Dy3+ ions, the emission intensity of Tb3+ ions show higher for 6mol% Tb3+ ions - doped oxyfluoride tellurite glasses. Based on Dexter theory, it is showed that the energy transfer between Dy3+ ions and Tb3+ ions was nonradiation energy transfer by analyzing the analyzingenergy level diagram and energy transfer from Dy3+ ions to Tb3+ ions.

In order to solve the low accuracy of the parameter identification of photovoltaic cell five-parameter double-diode model, a artificial bee swarm algorithm was proposed.The method is to use the idear of the cure fitting to calculate parameters.In order to make a comparison of the normalized root mean square error percentage,the calculation of current value must be identified.In order to make double-diode model equation contain only one variable in index factors,the method of variable substitution is adopted.Through the programming,the calculation of current values can be identified.The normalized root mean square error percentages of artificial bee swarm and New-Raphson method are 0.011 7% and 6.35%.The experiment and analysis show that the accuracy of artificial bee swarm algorithm is better than New-Raphson method,genetic algorithm,pattern search algorithm and simulated annealing algorithm to solve the accuracy of parameters,which can be considered as a new method to provide for parameter identification of photovoltaic cell.

The principle and key technology of balance detcetor for coherent optical communication were analyzed.A set of high-speed balance detection system was designed,and the coherent optical communications test platform was built indoors.Actual tests show that the balance detector can achieve the different rate of coherent detection,which can provide an essential support for coherent optical communication.Under 2.5 Gbps,the sensitivity can be obtained -26 dBm under the condition of direct detection using single pipe,where dynamic range is -26-3 dBm.When the power of local oscillator laser is 3dBm,coherent detection sensitivity can reach 46.5 dBm,where dynamic range is -46.5-3 dBm.

The Geiger-mode APD is very sensitive. For this advantages, it is widely used for astro-observation, particle physics, LIDAR. Sky background noise is a big problem for Geiger-mode APD detector during the day. The detection statistical model in theory was built, False alarm probability and detection probability and finding the way to increase maximum detection distance in difference detection threshold and background noise were discussed. In difference background noise, the maximum detection distance was determined. By limiting the filter bandwidth or reducing the detector open time, the background noise photon number is reduced to 2. The success rate of detection at 900Km is 96.6%. To the non-cooperative target, when the radar scattering cross section is 1 m2, the success rate of detection is 70%.

According to the extended Huygens-Fresnel principle and Collins formula, based on complex Gaussian function expansion method, the cross-spectral density formula of elliptically polarized Gaussian Schell-model beam passing through the rectangular aperture was derived. Meanwhile combined the Stokes vector theory, the expressions of light intensity, the degree of polarization, the orientation angle and the degree of ellipticity on the receiver plane were studied. Furthermore, the effects of diaphragm aperture obscuration ratio on the light intensity, the degree of polarization, the orientation angle and the degree of ellipticity were analyzed. The results show that the light intensity and polarization properties of polarized Gaussian Schell-model beam passing through the aperture exhibit variation with oscillations, and effects of aperture obscuration ratio on them are drastic, especially in the near-field region. Besides, with the increasing of the transmission distance, effects of the aperture on the light intensity and polarization properties are reduced.

The spectral element combined with precise integration method was used to simulate and analyze the waveguide discontinuities with anisotropic dielectric.With the variational principle based on single variable corresponding to the vector wave equation,spectral elements,a special type of higher order finite element with sampling points defined as the Gauss-Lobatto-Legendre points,were employed to discretize the cross section of the waveguide structure,which contains anisotropic dielectric.Then the semidiscretized problem was cast into Hamilton system and sloved by the precision integration method.With adopting the spectral elements,high precision of calculation results can be obtained under the low number of unit grids;With the precise integration method,the longitudinal length of structure can be set arbitrarily.It can overcome the weakness of increasing computation amounts as lengthening the distance from artificial boundary to dielectric block.Results show that semi-analytical spectral element method can be used to effectively solve waveguide discontinuities problems,which contains anisotropic dielectric.The proposed methords is demanstrated to solve waveguide discontinuities problems with high computational accuracy and efficiency.

The controlling of the distributions of intensity and transversal energy flow in the focal filed of azimuthally polarized beams by multiple parameters was presented. The modulations of non-uniform spiral phase and rotationally symmetric amplitude obstacle on the focusing properties of azimuthally polarized beams were numerically studied,as well as their combined modulation on transversal energy flow and polarization distributions in the focal plane were also analyzed,based on the vectorial diffraction theory. The results demonstrate that the non-uniform spiral phase has significant effects on the focusing properties,and give rise to the shift of gravity of the focused field. With the combined modulation of even-fold rotationally symmetric amplitude obstacle,local elliptical polarization and circular polarization,as well as transversal energy flow appear in the focused field. Additionally,adjusting the phase structure not only can control the gravity of the focused field,but also can further enrich the focal field polarization state and transverse energy flow. This method of controlling the intensity and energy flow of focused field provides a new way to realize the manipulation of particles in special area.

Enlightened by the degree of paraxiality that was recently introduced by Gawhary and Severini in Opt.Lett.33,1360(2008),a parameter,called the degree of diffraction,is defined to describe the diffractive spreading of a monochromatic light beam.This is a parameter that is independent of the degree of paraxiality.Nevertheless,the same as the degree of paraxiality,the degree of diffraction depends only on the angular spectrum of a beam.With this definition,it is ready to compare quantitatively the diffractive spreading of different beams.-WUJie|jiewu@shu.edu.cn