ИСТИНА

Interaction of high-power mid-infrared laser pulses with matter is actual and interesting challenge of modern physics. The key factor is the development of laser systems operating at the spectral range specified. In order to obtain relativistic intensities, along with an increase in energy and shortening the duration of laser pulses it is necessary to control the shape of the wave front to minimize the area of the focal spot. The achievable focusing intensity could be significantly reduced due to various aberrations occurring during the pulse propagation through the optical system. To correct them, one can use a system consisting of deformable mirror and wave fronts sensors like Shack-Hartman sensor or lateral shearing interferometer. Unfortunately, there are no sensors with sufficiently high spatial resolution in the mid IR spectral range and they are too expensive. This work presents a system consisting of deformable mirror and pyroelectric array camera. This system works on the basis of a closed-loop technique using genetic algorithm or particle swarm method. Laser radiation with 3.9 mkm central wavelength was focused by 10- cm focal length parabolic mirror into the optical microscope. This microscope consists of two converging lenses enlarging the image of focal spot by a factor of 23. The signal from the sensor was processed by a program written in C# and using Labview environment. The program controls the deformable mirror by exposing various combinations of the first 12 Zernike polynomials. Using a genetic algorithm and a particle swarm optimization method, we managed to select the amplitudes in such a way as to minimize the beam area at the focus spot. The applied algorithms made it possible to achieve a beam size at the focus close to the diffraction limit, but the particle swarm method did it faster. According to our calculations, peak intensity increased by the factor of 1.5.