A mini adaptive optics system is developed in which a micro-machined membrane deformable mirror and the technique of cross-folded optical path are employed. The system has a volume of 30x20x10cm3, a weight of 4kg, while its bandwidth is 17Hz, and the accuracy of its wave-front sensor is ?/15 mis. The system is aimed at improving the image quality of space-based optical systems, but it is versatile. The control host is a PC computer, and various functions are realized, such as, real time display of image or wave-front, testing of the response matrix of the deformable mirror, and closed-loop control. An experimental system is also setup to test the performance ofthe AO system. The results of the experiments show that the AO system is very effective in compensation for thermal deformations and dynamic disturbances.

We have constructed and integrated a 61-element adaptive optics system at the 1.2m telescope of Yunnan Observatory in China. It provides compensated images in visible wavelengths and consists of a tip-tilt mirror, a 61 actuator deformable mirror, a visible Hartmann-Shack wavefront sensor with gated, a tip-tilt sensor, and controller. This paper will present some images taken with this adaptive optics system and describe the performance measured at the telescope.

The performance of low-order adaptive optics compensation for extended object is briefly analyzed theoretically. Several series of short exposure images and simultaneous wavefront sensor data at the Vacuum Tower Telescope at Sacramento Peak were collected to validate the low-order adaptive optics compensation for low contrast extended object, including solar granulation and sunspot, by using deconvolution from wavefront sensing (DWFS). The results show the low-order adaptive optics compensation is very effective for low contrast extended object.

In this paper, correlation tracker for tilt-correction adaptive optical system at Solar Tower of Nanjing University built by the Institute of Optics and Electronics, Chinese Academy of Sciences, is described. The absolute difference algorithm is used to detect the image motion in the correlation tracker. The hardware configuration and timing of the correlation tracker are shown in detail. Furthermore, the experimental results are presented.

Astrodynamical Space Test of Relativity using Optical Devices (ASTROD) is a newly proposed space mission with deep space laser ranging. Its scientific goals are to measure the relativistic parameters with 3-6 order better sensitivity. The Mini-ASTROD is a down-scaled version ofthe ASTROD. The laser ranging with a distance of 1 or 2 AU between the spacecraft and the ground station will be performed. So the turbulence effects for the laser beam propagation must be considered. A new idea of the real-time tilt correction of the laser beam on the ASTROD and the Mini-ASTROD is proposed. The technical plan for this purpose at the laser ranging system of Yunnan Observatory 1 .2m telescope is introduced in this paper.

Recent studies on laser beam propagating over a long distance through even weak atmospheric turbulence have shown that under conditions where scintillation is significant a continuous phase function does not in general exist, owing to the presence of branch points in the complex optical field. The scintillation can create problems when one is using an adaptive-optics system for atmospheric-turbulence compensation. Significant degradation was observed in the adaptive-optics correction through the results of our simulated experiments with a wave-optics code as the scintillation increased when the Fried parameter r0 remained a constant. As result of the measured gradient field (i.e., idealized pointwise phase differences measurements) including two components, one that is expressed as the gradient of a scalar potential and the other that is expressed as the curl of a vector potential, the scalar and vector potentials are both easily reconstructed from the measured gradients. The total potential (including the scalar and vector potentials) and the scalar potential serve as an upper bound on the performance of Hartmann-sensor reconstruction and Hartmann-sensor-based least-squares reconstruction, respectively. The results obtained illustrate that scintillation effects are not significant until the Rytov number is greater than 0.2. When the Rytov number is greater than 0.2, the performance of adaptive-optics correction is obviously degraded. These computational results showed that the compensative effect of adaptive optics is not characterized completely by Fried parameter. The effect of scintillation needs to be considered in compensation of adaptive optics when a laser beam propagated over a long distance through even weak atmospheric turbulence.

We propose equal output power dividers using nonlinear waveguide structure. By adjusting the branch angle, input power and the nonlinear coefficient, they could provide equal output power in each branch. The numerical analyses show that the results are correct.

Stimulated Brillouin Scattering (SBS) is an important means to achieve optical phase conjugation beam, which has the characteristics of self-pumping, producing phase conjugation wave and compensating wave-front aberration. Using SBS in glass fibers as phase conjugator, the field of application of SBS phase conjugation can be expanded, for fibers can offer low power threshold and stable behavior even at high peak and average input power. In this article, phase conjugation based on SBS in undoped multimode quartz fibers was observed. With the 13-15ns pump beam at 1.06 µ m wavelength from a Q-switched Nd:YAG laser, the reflectivity of SBS for the fibers with core diameter of 100 µ m and 62.5 µ m and different length was characterized at different input energy and lens focal length, considering of the reflection loss at the fiber surface. The reflectivity during the SBS process, affected greatly by system parameters, was measured no more than 70% due to saturation. The waveform of SBS was recorded and investigated. With the change of the waveform at the fiber length changing from 1.6m to 0.6m, the pulse duration of SBS decreased from 5ns to 2ns. The multi-peak modulation did not occur, which indicated that SBS had taken place in stable condition. Based on these experiments, some references to control SBS waveform were put forward.

Based on numerical solution of the theoretical mode for the SBS process in a novel multimode fiber, the power distributions of coupled light and sound wave in an internally tapered fiber and during pulse persistence have been shown in this paper. Compare with a common fiber PCM, it's found that the energy threshold of SBS procedure in tapered fiber can decrease greatly to a few micro-joule while maximum SBS reflectivity can theoretically arrive to 98% and the dynamic-range is expended largely. In addition, the phenomenon of the power modulation of Stokes wave is explained, and a very narrow Stokes pulse with high peak power can be achieved with the optimizing fiber parameters.

A detail description of a new liquid crystal lens is presented. The focal length of the lens is a function of the applied voltage. The working mechanism of the liquid crystal lens is explained. The lens acts as a magnifying glass is demonstrated as an example.

Phase compensation effectiveness and long time period working stability are two most important performances of an adaptive optics (AO) system. Effects of reconstruction matrix and controller coefficients on these performances are investigated by means of a pure numerical simulation in this paper. A new modified reconstruction matrix is proposed and compared with other existing matrixes in practical application. It is shown that the recently proposed reconstruction matrix can produce better phase compensation results and much better long time period working stability in an AO system. Different reconstruction matrix can greatly affect the long time period working stability under certain conditions. Under some conditions, an AO system with a reconstruction matrix can work stably in a quite long time period, but a working instability can occur in a super-long time period. It is found that the controller coefficients have even greater effect on the long time period working stability in an AO system. The controller coefficient ?1=1.00 is a marginally stable (sub-stable) condition for an AO system. When ?1<1, the long time period working stability of an AO system is much improved.

The beacon problem of Adaptive Optics (AO) is settled by the promotion of laser-guide-star (LGS), but the anisoplanatic error due to LGS will degrade the performance of AU system as well. Analytical expressions are given to evaluate the modal anisoplanatic enor of atmospheric turbulence for LGS. Anisoplanatic error for Rayleigh LGS and Na LGS are also analyzed. Results show that the modal anisoplanatic error of 90 km Na LGS is obviously less than that of 15 km Rayleigh LGS without the angle deviation between LGS and object, but is greatly sensitive to the angle deviation than Rayleigh LGS. Good performance will be obtained with low-order abenation mode correction in LGS AOS, and when angle deviation between beacon and object is larger than isoplanatic patch, low-order modes should be corrected for effective correcting result.

Curvature sensing is a technique that provides the phase of wavefronts through measurements of irradiance in well defined planes along a beam of light. The equation describing the propagation of intensity and phase is well known; here the profile of a collimated monochromatic beam is determined at a certain longitudinal position by measuring the irradiance pattern at two planes either side of that position. Using a distorted grating lens, the intensity profiles of the two planes can be recorded simultaneously. Their difference may be related back to the wavefront phase either through solutions of the Intensity Transport Equation. The theory and first experimental results are reported.

It is well known that noise and detection error can affect the performances of an adaptive optics (AO) system. Effects of noise and detection error on the phase compensation effectiveness in a dynamic AO system are investigated by means of a pure numerical simulation in this paper. A theoretical model for numerically simulating effects of noise and detection error in a static AO system and a corresponding computer program were presented in a previous article. A numerical simulation of effects of noise and detection error is combined with our previous numeral simulation of a dynamic AO system in this paper and a corresponding computer program has been compiled. Effects of detection error, readout noise and photon noise are included and investigated by a numerical simulation for finding the preferred working conditions and the best performances in a practical dynamic AO system. An approximate model is presented as well. Under many practical conditions such approximate model is a good alternative to the more accurate one. A simple algorithm which can be used for reducing the effect ofnoise is presented as well. When signal to noise ratio is very low, such method can be used to improve the performances of a dynamic AO system.

The Zernike modal wavefront reconstruction error of Shack-Hartmann sensor on measuring the atmospheric disturbed wavefront was analyzed in this paper. It's showed that the wavefront reconstruction error is concern with sub-aperture configuration type and the total Zernike mode number used in wavefront reconstruction algorithm. Some formulas to calculate the wavefront reconstruction error of a Shack-Hartmann sensor in Kolmogorov turbulence were deduced in this paper too. The experiment data from two Shack-Hartmann sensors with configuration of 8x8 sub-apertures and 32x32 sub-apertures respectively were analyzed and compared.

Interferometry is a successful method of measuring fields of refractive index and displacement. It therefore has many applications in the measurement of fluid flows, photo elastic stresses, and surface and vibration analysis. The Fourier transform method of interferogram analysis is a useful mean of extracting phase information from linear fringe patterns generated by the interference of tilted wave fronts. This paper introduces Fourier transform method, and the results are given by applying the method to recovery ofthe original wave front in lateral-shearing interferometry.

The interferometer can measures accurately a static or dynamic wavefront . It can be done using a system of circular radial shearing interference with spatial phase modulated. Because the method only needs one frame interferogram so that can rejected the effect of vibrations and noises. The wavefront errors measured make adaptive optic system (AOS) that contain a deformable mirror correct the wavefront aberrations again. This paper described a system of radial shearing interference with spatial phase modulation. It is based on the Fourier transform method that the analysis and data processing of the interference fringe pattern with suitable linear carrier. An algorithm of shearing wavefront reconstructed can obtain the original wavefront. The system of diagnostics can check the operation of the AOS and quantify laser beam quality. Finally, the interference experiment and data processing results have been given in this paper.

A novel method named radial slope testing for measuring the wave aberration of an optical imaging system with a large aperture is introduced, which is a kind of self referenced testing. A Zernike slope polynomial fitting algorithm is applied to the data processing. The principal of method and construction of system are described, the results of computer simulation testing are presented as well. It is shown that this method is especially useful for wavefront sensing of an active optical system operated on a satellite without any guide star or reference surface.

By using the time-dependent propagation computer code, adaptive compensation for thermal blooming effects, which are induced by collimated high-energy laser (HEL) beam propagation through the atmosphere, is numerically calculated and analyzed under different conditions. The numerical results show that, with the definite adaptive optics (AO) system, the scaling parameter NJY'NFB is available to evaluate the effect of adaptive compensation efficiently. Moreover, we get the scaling relation between the scaling parameter ND/NFB and the far-field Strehi ratio, which is can be described by Strehl=1/[1+AND/NFB+B (ND/NFB) C] where A, B and C are fitting parameters. We also get the threshold of adaptive phase compensation instability (PCI) through analysis ofthe scaling relation above. In addition, we discuss the difference between adaptive compensation and whole-beam compensation.

A combination of a Hartmann-Shack sensor and a standard far-field measurement on one single detector is proposed. The technique is fast, manages without moveable parts, permitting a very compact desing. It is not only suited for characterisation of the wave-front distribution, but may also be considered for determination of the important parameters beam with, beam divergence and beam propagation ratio m2 of partially coherent laser beams. First results indicate that a fairly thorough beam characterisation including spatial coherence, propagation characteristics and beam quality cam be achieved with thi method.

The disadvantage in expanding dynamic range and restraining noise of the traditional H-S (Hartmann-Shack) wavefront sensor centroid computation method is analyzed. Based on the temporal characteristic of atmosphere turbulence, through determining the changing scope of centroid motion between two adjacent sample periods, a new dynamic tracking centroid method of H-S wavefront sensor is proposed. Using this method, the dynamic range of wavefront sensor can be expanded when atmosphere turbulence is strong; the effect of CCD readout noise and shot noise can be reduced.

A new heuristic optical scintillation model developed recently is viewed and it is a available method in investigation on laser beams propagation in turbulent atmosphere. The irradiance scintillation is treated as a modulation of small scale scintillation by large scale scintillation as laser beams propagation in turbulent atmosphere, the irradiance scintillation is investigated for uplink propagation at various receiving heights and zenith angles for different atmospheric turbulence model. The influences of receiving height and zenith angle on the irradiance scintillation is analyzed for different atmospheric turbulence model, and the conclusions deduced are useful for farther future researches.

The temporal spectra of the intensity fluctuations of Gaussian beam waves propagating through a Kolmogrov turbulence are analyzed numerically. It is found that high-frequency spectra (HFS) are mainly determined by a parameter ? that is proportional to the square ofthe ratio ofthe Fresnel size and the beam radius on the receiver. A plane or spherical wave assumption can be made only for a beam with very small A, and the HFS presents a —8/3 power-law dependence. For a beam with moderately small ?, the HFS presents a —8/3 and a —14/3 power-law dependence in two regions. For a beam with ? being about or greater than unity the HFS presents a unique —14/3 power-law dependence. The results are verified by experimental data.

Thermal blooming is one of the most important factors, which make the beam diffused and cause the decline of laser intensity on the object. This paper presents a method to reduce thermal blooming of high-energy laser (HEL) in the beam tube and compares two models describing the thermal blooming. Helium has the qualities of low absorption coefficient, high thermal conductivity and low index of refraction, and can be used as the medium through which HEL beam propagates. The condensations of thermal conduction model and acoustic wave model are evaluated respectively. Results show the method is practicable, and two models' applicable ranges are got.

In order to examine the performance of adaptive optics system in the laboratory environment, a new simple laboratory atmosphere turbulence simulator (ATS) is developed which uses the hot resistance coil to generate the hot air turbulence and the fan to control the intensity of the turbulence. The spatial and temporal characteristics of the turbulence generated by the ATS are tested in different experimental conditions by the test system and then compared with the theoretical Kolmogorov spectrum atmosphere turbulence. The results show that the spatial and temporal characteristics of the turbulence generated by ATS have definite similarity with the Kolmogorov atmosphere turbulence under certain experimental conditions. Finally the reason of the difference with theory Kolmogorov atmosphere turbulence is analyzed.

Laser scintillation in the atmosphere exhibits fractal behavior. Two fractal characteristic parameters, the fractal dimension and the Hurst coefficient, are analyzed and compared with two traditional parameters, the scintillation index and the scaling exponent of the power spectrum. Results show that the scintillation is a kind of non-stationary process with long-run dependence; under the saturated scintillation conditions, the values of the two-fractal parameters are mostly smaller than those under weak scintillation conditions. According to the statistical behavior of the fractal parameters, it is possible to find new ways to deal with some problems concerning the scintillation saturation.

A novel rapid laser electro-optical scanning system is studied. Theoretical and experimental analysis shows the feasible ofthe system. Based on the theory of optical phased array, the operating characteristic of the electro-optical waveguide array scanner, the core part of the rapid laser electro-optical scanning system, are specifically investigated. According to the theoretically result of the design parameters of the electro-optical waveguide array scanner, a 4 waveguides array is fabricated by use of AlGaAs crystal through MOCVD. By using of a designed device, steering of laser beam is realized. Experimental results of the A1GaAs-based optical scanner conformed the performance of the scanning system, such as rapid scanning (0~10MHz) and wide scan zone (30 Deg).

The effect of transverse coupling in a photorefractive oscillator is studied, from which the condition for stable optical patterns of multimode oscillation is given analytically and verified by numerical simulation. Out of the stable condition, the period-doubling route to spatiotemporal chaos is observed.

Wave-front distortion compensation using system performance metric optimization applied to ground-to-air carbon-dioxide laser communication system is explored theoretically and experimentally. A performance criterion for parallel perturbation-based algorithms is introduced and applied to optimize adaptive system architecture. We present numerical simulation results for an adaptive imaging system based on the stochastic parallel perturbation technique, along with 37 control channels. An adaptive system with a self-organized control channel hierarchy i introduced and analyzed. Results demonstrate that adaptive wave front correction by the parallel perturbation technique can significantly improve imaging quality.

The image motion in the focal plane of the Space Solar Telescope (SST) can be compensated essentially by means of a correlation tracker. The method is based on determining, in real time, the relative displacements between successive images ofgranulation, by means ofcorrelation techniques. This paper reports on a simulation system, which used to simulate the satellite attitude of the SST. An overview of the complete system including optical design, system analysis, etc. is shown together with preliminary results. Using this simulation system, we demonstrate the correlation tracker really work under the estimated satellite condition.

Using an actuator array to thrust load onto the back of a mirror can control the profile of the mirror or correct its residual irregularity. It is meaningful to study how to improve the control or correction capability of active mirror for practice. The closest profile of a mirror to a given Zernike element profile can be obtained through linear combination of the influence functions. The algorithm of evaluating an active mirror's capability of correction is presented. Static analysis via Finite Element Method (FEM) is studied at various conditions with different amount and distribution of actuators, as well as the fixing manner, and the optimum scheme of actuator array is yielded.

The Shack-Hartmann sensor is used for wavefront sensing in adaptive optics. In the conventional use of the Shack-Hartmann sensor, information on the components other than wavefront tilt cannot be obtained. This means that the value of the Strehl ratio of the compensated image is not so high in spite of the fact that the Shack-Hartmann sensor images have higher order information about the global wavefront. We propose to use both the Shack-Hartmann sensor images and the image in the focal plane of the global wavefront as the constraints in the iterative Fourier transform algorithm proposed by J.R.Fienup. The reconstructed wavefront by using only the information on the gravity center of an image of the Shack-Hartmann sensor is used as an initial estimate in this iterative procedure. The effectiveness of this proposed algorithm is shown by computer simulation results. This proposed algorithm converged to an adequate wavefront rapidly without suffering from the stagnation problem and it showed good performance even in the case in which measured images were contaminated by photon noise.

The initial theory for a novel type of wavefront controller for microwaves is described. This controller is based on the principle that the effective refractive index of a structure is a square root product between the permittivity and permeability of a material, n = ??µ. With high conductivity metals, such as silver, light acquires an effective mass so that the longitudinal mode has a finite frequency known as the plasma frequency, ?p. B elow that frequency the dielectric function is negative, allowing no modes in the bulk of the metal. This is responsible for the amazing and unique properties of structured metals. One may, by extension of scale, design a metallic structure whose effective is negative, for wavelengths longer than the structure’s unit cell. Such structures have been suggested recently by Pendry et al. The symmetry of Maxwell’s equations implies that magnetic structures can be engineered from non-magnetic materials, so that an effective ? is produced down to negative values. An example of such a structure is investigated here in detail. I also discuss how the electric and magnetic structures are combined to produced a controllable refractive index over the unit cell, implying that we can construct wavefront controllers from conductive mesostructures.

A new center position detecting algorithm of the spot image for the Shack-Hartmann wavefront sensor was developed. The new algorithm is a modified center of weight algorithm, which uses some power of the grey level intensity of the spot images instead of thr grey level intensity itself of the spot images. From experiments, the repeatability and accuracy of the center position detection of the spot images of the Shack-Hartmann wavefrond sensor which used the new algorithm were improved compared with the conventional center position detection algorithm using the center of weight. Applications of the algorithm to measurement of the displacement of the spot images and the Shack-Hartmann wavefront sensor for measuring wavefornt distortion and the experimental results of closed-loop wavefront correction are described in this paper.

The variations of group velocities for Gaussian beams under different hypotheses were studied, and the rationality of the results were discussed and analysed. Then we show that the beam waist radius should be proportional to the square root ofwavelength. Under this condition, the group velocities are all equal to c on the beam axis and smaller than c off the axis.