High-spatial resolution stacked-actuator deformable mirror for correction of atmospheric wavefront aberrations.

Deformable mirrors are vital components of any adaptive optical system. Considering such a crucial role in compensation of incident wavefront distortions, the main requirements are imposed on these elements that determine performance of the entire system. To correct for phase distortions in high-power laser complexes a stacked-actuator deformable mirror with water cooling was developed. The main characteristics of the mirror, such as the initial surface profile (flatness), response functions of the actuators, maximal stroke, and amplitude-frequency characteristics are presented in this paper. Experimental investigations of the proposed cooling method of the mirror surface through actuators were performed.

Real-time 1.5 kHz adaptive optical system to correct for atmospheric turbulence.

Problems of constructing an adaptive optical system intended for correcting the wavefront of laser radiation that has passed through a turbulent atmosphere are considered. To ensure high-quality wavefront correction, the frequency of the discrete system should be at least 1 kHz or more. This performance can be achieved by using FPGA as the main control element of the system. The results of a laboratory experiments of the laser beam phase fluctuations caused by turbulence, produced by the airflow of a fan heater, correction by means of the FPGA-based adaptive optical system are presented. The system efficiency was evaluated at various correction frequencies up to 1875 Hz.

Laser beam focusing through a moderately scattering medium using a bimorph mirror.

The rarely considered case when the optical radiation passes through the weakly scattering medium, e.g. mid-density atmospheric fog with the number of scattering events up to 10 was investigated in this paper. We demonstrated an improvement of focusing of a laser beam (λ=0.65 µm) passed through the 5 mm-thick layer of scattering suspension of 1 µm polystyrene microbeads diluted in a distilled water. For the first time the low-order aberration corrector - wide aperture bimorph deformable mirror with 48 electrodes configured in 6 rings was used to optimize a far-field focal spot. We compared efficiencies of the algorithm that optimized the positions of the focal spots on Shack-Hartmann type sensor and the algorithm that optimized the peak brightness and the diameter of the far-field focal spot registered with a CCD. We experimentally demonstrated the increase of the peak brightness of the far-field focal spot by up to 60% due to the use of the bimorph deformable mirror for beam focusing through the scattering medium with concentration values of scatterers ranged from 105 to 106 mm-3.

Bimorph deformable mirror with a high density of electrodes to correct for atmospheric distortions.

This paper presents a new development of small-diameter, high-spatial-resolution, semipassive bimorph deformable mirrors to be used in different imaging systems. To manufacture the small control elements, laser engraving technology is used. An ultrasonic welding technique to connect the wires to the electrodes (actuators) is applied for this kind of mirror. The initial flatness of the mirror surface equals 0.33 µm (P-V) due to the use of substrate polishing technology after gluing the glass substrate to a piezo disk. We present the main parameters of these wavefront correctors, such as the response functions of different electrodes, temporal behavior, and the ability to compensate for high-order aberrations.