ABSTRACT
This article presents a study of the electrophysical properties of a piezoceramic material for use in adaptive optics. The key characteristics that may be important for the manufacturing of piezoelectric deformable mirrors are the following: piezoelectric constants (d31, d33, d15), capacitance, elastic compliance values s for different crystal directions, and the dielectric loss tangent (tgδ). Based on PZT ceramics, the PKP-12 material was developed with high values of the dielectric constant, piezoelectric modulus, and electromechanical coupling coefficients. The deformable mirror control elements are made from the resulting material-piezoceramic combs with five individual actuators in a row. In this case, the stroke of the actuator is in the range of 4.1-4.3 microns and the capacitance of the actuator is about 12 nF.
ABSTRACT
The use of the post-compression technique ensures gain in laser pulse peak power but at the same time degrades beam focusability due to the nonlinear wavefront distortions caused by a spatially nonuniform beam profile. In this paper a substantial focusability improvement of a post-compressed laser pulse by means of adaptive optics was demonstrated experimentally. The Strehl ratio increase from 0.16 to 0.43 was measured. Simulations showed that the peak intensity in this case reaches 0.52 of the theoretical limit.
ABSTRACT
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.
ABSTRACT
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.
