Xingkun Ma

Experimental investigation of the deformable mirror with bidirectional thermal actuators

A deformable mirror with actuators of thermoelectric coolers (TECs) is introduced in this paper. Due to the bidirectional thermal actuation property of the TEC, both upward and downward surface control is available for the DM. The response functions of the actuators are investigated. A close-loop wavefront control experiment is performed too, where the defocus and the astigmatism were corrected. The results reveal that there is a promising prospect for the novel design to be used in corrections of static aberrations, such as in the Inertial Confinement Fusion (ICF).

High-precision system identification method for a deformable mirror in wavefront control

Based on a mathematic model, the relation between the accuracy of the influence matrix and the performance of the wavefront correction is established. Based on the least squares method, a two-step system identification is proposed to improve the accuracy of the influence matrix, where the measurement noise can be suppressed and the nonlinearity of the deformable mirror can be compensated. The validity of the two-step system identification method is tested in the experiment, where improvements in wavefront correction precision as well as closed-loop control efficiency were observed.

Wavefront correction performed by a deformable mirror of arbitrary actuator pattern within a multireflection waveguide

The wavefront correction ability of a deformable mirror with a multireflection waveguide was investigated and compared via simulations. By dividing a conventional actuator array into a multireflection waveguide that consisted of single-actuator units, an arbitrary actuator pattern could be achieved. A stochastic parallel perturbation algorithm was proposed to find the optimal actuator pattern for a particular aberration. Compared with conventional an actuator array, the multireflection waveguide showed significant advantages in correction of higher order aberrations.

Orientation dependent wavefront correction system under grazing incidence

Making use of the stretching effect of grazing incident laser beam, a novel method of wavefront correction was promoted. Without adding any extra beam expanding components, aberrations of wavefront could achieve satisfying correction by two grazing reflections along orthogonal directions on the deformable mirrors. The stretching effect expanded the beam size along grazing direction and the orientation dependent varying aberrations were well compensated as more actuators took effect in the correction process. Analysis showed that the fitting coefficient of all the first 30 order Zernike polynomials could be controlled within 5% by this method.

Location-grouping algorithm based on limited actuators deformable mirror for high precision wavefront aberration correction in adaptive optics system

The aberration in the center position of wavefront can be corrected well when the deformable mirrors (DM) used in high-resolution adaptive optics system of telescope. However, for the defocus and spherical aberration of telescope, the four corners of the wavefront cannot be corrected well. A novel correction method with different levels and regions of deformable mirror is proposed to solve this problem. The control elements of wavefront in four corners are divided. And every four or five DM units in one corner is in a group. Compared with conventional correction method, the location-grouping method showed significant advantages in correction of different order aberrations.

Development of a novel three-dimensional deformable mirror with removable influence functions for high precision wavefront correction in adaptive optics system

Deformable mirror is a widely used wavefront corrector in adaptive optics system, especially in astronomical, image and laser optics. A new structure of DM--3D DM is proposed, which has removable actuators and can correct different aberrations with different actuator arrangements. A 3D DM consists of several reflection mirrors. Every mirror has a single actuator and is independent of each other. Two kinds of actuator arrangement algorithm are compared: random disturbance algorithm (RDA) and global arrangement algorithm (GAA). Correction effects of these two algorithms and comparison are analyzed through numerical simulation. The simulation results show that 3D DM with removable actuators can obviously improve the correction effects.

Development of resonator analysis applied in hybrid slab laser with consideration of optical gain and thermal lens effect

By introducing the rate equations and light intensity propagating equations into the fast Fourier transform-based calculation, the optical gain served as the connection between the light field and light intensity, its influence over mode pattern was studied. Thermal lens effect was also investigated by means of finite element analysis. The analysis was applied to a slab laser with a hybrid cavity. A similar experimental study was also carried out in the laboratory. TEM(00) mode with sidelobes along the unstable direction was observed both in the calculation and experiment. As predicted in the analysis, the homogeneity of the pump light improved the beam quality. Numerical and experimental results of pump threshold and slope efficiency were also presented.