Pavel Romanov

Largest in the world bimorph deformable mirror for high-power laser beam correction

The deformable mirror with the size of 410x468 mm controlled by the bimorph piezoceramic plates and multilayer piezoceramic stacks was developed. The results of the measurements of the response functions of all the actuators and of the surface shape of the deformable mirror are presented in this paper. The study of the mirror with a Fizeau interferometer and a Shack-Hartmann wavefront sensor has shown that it was possible to improve the flatness of the surface down to a residual roughness of 0.033 μm (RMS). The possibility of correction of the aberrations in high power lasers was numerically demonstrated.

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.

Shack-Hartmann wavefront sensor versus Fizeau interferometer for laser beam measurements

The problem of wavefront measurements is one of the most important tasks in the modern optics and laser physics. There are lots of different tools for wavefront measurement. And the user might choose any type of instrument which could solve certain task. The devices for wavefront analysis differ from each other not only by setup and by processing algorithms but also dynamic range and accuracy should be taken into account. The most popular devices are Shack- Hartmann wavefront sensor and various types of interferometers. In this paper we compare Shack-Hartmann wavefront sensor with Fizeau interferometer; classical analysis of interferograms (based on measurement of the fringe centers position) and phase-shifting methods are also compared. Advantages and disadvantages of three methods are discussed.

Analysis of accuracy of shack-hartmann wavefront sensor measurements

Shack-Hartman wavefront sensor for scientific investigations of wave fronts is represented in paper. It was shown that this type of wavefront sensor has multifunctional possibilities to measure laser radiation. Aspects of accuracy measurements increasing and dynamic range expansion are discussed.Samples of schemas and results of wavefront measurements to high power solid state lasers are presented.

Adaptive system for high power lasers

This paper presents the novel optical closed-loop adaptive system (CLAS) for compensation of the laser beam aberrations and results of its application in high power lasers. A closed-loop adaptive algorithm is developed to control for a continuous-surface deformable bimorph mirror. The control voltages applied to the electrodes reduce the wavefront distortions measured by a Shack-Hartmann wavefront sensor (SHWS). Adaptive system can correct the low-order aberrations with the frequency is about 25 Hz. The amplitude of corrected aberrations is about 10 microns and sensitivity is about 0.08 microns. The examples of the use of such systems to control for radiation of TW Ti:Sa lasers are presented.

Comparative analysis of methods and optical-electronic equipment to control the form parameters of spherical mirrors

In this paper we consider two approaches widely used in testing of spherical optical surfaces: Fizeau interferometer and Shack-Hartmann wavefront sensor. Fizeau interferometer that is widely used in optical testing can be transformed to a device using Shack-Hartmann wavefront sensor, the alternative technique to check spherical optical components. We call this device Hartmannometer, and compare its features to those of Fizeau interferometer.

Extremely large bimorph deformable mirror for high intense laser beam correction

Two types of the large bimorph deformable mirrors with the size of 410x468 mm and 320 mm were developed and tested. The results of the measurements of the response functions of all the actuators and of the surface shape of the deformable mirror are presented in this paper. The study of the mirror with a Fizeau interferometer and a Shack- Hartmann wavefront sensor has shown that it was possible to improve the flatness of the surface down to a residual roughness of 0.033 μm (RMS). The possibility of correction of the aberrations in high power lasers was numerically demonstrated.

Adaptive optical system with water-cooled bimorph deformable mirror

The water cooled deformable mirror of the bimorph type is intended for beam correction in the CW solid state laser with output power of 10 kW level. An operation of the adaptive system using Shack-Hartmann wavefront sensor and deformable mirror is based on the phase conjugating algorithm. The first results will be presented in this report.

The commercially available version of Shack-Hartmann wavefront sensor

The development of low-cost Shack-Hartmann wavefront sensor (SHWS), based on USB2-interface of CMOS camera, is presented in this report. The description of main principle of SHWS and example of wavefront measurements are given. A comparative characteristics and spheres of sensors applications, based on USB-2 and IEEE-1394 types interfaces, are shown below. But certainly there are advantages and disadvantages of each type of these sensors. That is why each type has more suitable spheres of application. This is the subject of our discussions.