Vadim Samarkin

Wavefront compensation method using a Shack-Hartmann sensor as an adaptive optical element system

This paper considers the use of an adaptive optical system for compensating aberrations of a laser radiation wavefront. Bimorph mirrors are used as correctors, and the wavefront is measured by a Shack-Hartmann sensor. Disadvantages of this adaptive system and ways to overcome them are discussed.

Deformable mirrors for laser beam shaping

Bimorph mirrors for laser beam correction and formation were developed and investigated. Different types of substrates and active piezoceramics materials were considered to fabricate temperature independent shape of the mirror surface and to maximize the sensitivity of the mirror. High reflectivity coatings for different wavelengths were studied.

Novel development of tiny bimorph mirrors

The main disadvantage of contemporary bimorph flexible mirrors is that they used to have rather large aperture. At the same time semipassive bimorph flexible mirror is one of the most widely used devices in various adaptive systems. We present a novel approach of multilayer bimorph (multimorph) mirrors and a numerical model to simulate them, based on a variation approach of the finite elements method in order to reduce the size (diameter) of these wavefront correctors. The multilayer bimorph mirror consists of a substrate and a number of piezoceramic layers. The electrode grid of each layer is determined separately to reproduce low order aberrations. We also present our results in reproduction of the wavefront phase dislocations (vortices) with the help of tiny bimorph mirror.

Laser beam formation by adaptive optics

This paper discusses the novel adaptive optical closed loop system with water-cooled bimorph mirror as a wavefront corrector to compensate for the aberrations of high-power CW laser beam. Shack-Hartmann wavefront sensor is used as an element for feedback control. Comparison of phase conjugation and modified hill-climbing technique is shown.

Problem of Shack-Hartmann wavefront sensor and interferometer use while testing strongly distorted laser wavefront

It is very important to analyse phase ingomogenity of high-power laser beam. Usually Shack-Hartmann wavefront sensor or interferometer is used to test both laser beam aberrations and quality of the optical element surface. But we found out that in case of strong distortions the measured aberrations differ from the real ones. To investigate this problem we used bimorph deformable mirror to introduce strong aberrations to the laser beam. The results of our experiments are discussed.

Screw Phase Dislocation Formation by Means of Flexible Bimorph Mirror

Formation of the given laser beam intensity and phase is important to solve practical and scientific problems. Bimorph flexible mirror is one of the most widely used devices for this purpose. In the work we present results of numerical and experimental formation of the vortex beam by means of the bimorph flexible mirror. To determine the required electrode grid we have developed a unique algorithm that allows finding the best suited semipassive bimorph mirror electrode spacing for reproducing almost all arbitrary specified phase profiles

Wide aperture (more than 500 mm) deformable mirrors for high power laser beam correction

Wide aperture bimorph mirrors for laser beam correction and formation were developed and investigated. Different types of substrates and active piezoceramics materials were considered to fabricate temperature independent shape of the mirror surface and to maximize the sensitivity of the mirror. High reflectivity coatings for different wavelengths were studied.

Hill-climbing algorithm for adaptive optical system with Shack-Hartmann sensor

We describe multi-dither adaptive optical system based on Shack-Hartmann wavefront sensor. RMS of the wavefront is minimized to get the best correction of the aberrated laser beam. Hill-climbing algorithm is used to determine voltages to be applied to the electrodes of a bimorph mirror which is used as a wavefront corrector.

Bimorph flexible mirror for vortex beam formation

We present a novel algorithm of bimorph mirror grid determination. Its usability is demonstrated on practical examples of defining electrode grid to form a vortex beam. We briefly describe the developed finite element bimorph mirror model, designed to evaluate an arbitrary electrode response function.

Beam characteristics of CO2 laser with controllable output mirror

The generation regimes of cw-pumped CO2 laser with the controllable base Fabry-Perot interferometer (FPI) as the resonator output mirror were investigated. The pulse-periodical radiation regime over the frequency range 0 - 5 kHz and pulse length range 0.1 - 10 ms with the modulation depth 100% were obtained. The FPI-based method of power control and stabilization was realized.