Alexander Nikitin

A device based on the Shack-Hartmann wave front sensor for testing wide aperture optics

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

Laser beam focusing through the scattering medium-low order aberration correction approach

Laser beam focusing (λ = 0.65 μm) through the scattering suspension of polystyrene microspheres in distilled water was investigated. Shack-Hartmann sensor was used to measure the local slopes of the Poynting vector, the CCD camera was used to measure the far-field focal spot’s intensity. Numerical and experimental investigations of focusing efficiency of the two bimorph deformable mirrors with 14 and 48 control channels were performed.

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.

Adaptive optical system for laser beam formation

The process of remapping the intensity profile of a laser beam is presented. Bimorph deformable mirror was used to change the beam phase; the control signals for the mirror were calculated in accordance with both phase analysis and far-field intensity distribution measurements.

Comparison of the efficiency of laser beam focusing through the scattering medium using 14- and 31-channel bimorph mirrors

We investigated the ability to focus laser beam (λ = 0.65 nm), propagated through the scattering suspension of polystyrene microspheres in distilled water, by means of two bimorph mirrors. Shack-Hartmann sensor was used to measure the local slopes of the Poynting vector, and the CCD camera was used to measure the intensity of the focal spot in the far-field. Correction efficiency of the two bimorph deformable mirrors — with 14 and 31 control channels — were compared. Numerical and experimental investigation of the focusing improvement of the laser beam propagated through the scattering medium was performed.

Formation of the doughnut and Super-Gaussian intensity distribution by means of different types of wavefront correctors

The transformation of an intensity distribution from Gaussian to a flattop, doughnut, etc. still is a very interesting and important task. And the necessary result could be obtained with the use of adaptive optics that changes the phase of the beam and modifies the shape of the focal spot in the far-field zone. In this paper, we present the flattop and doughnut beam formation result with the use of a bimorph and stacked-actuator deformable mirrors as well as LC phase modulator. The experimental results are also given.

LC phase modulator vs deformable mirror for laser beam shaping: what is better?

The latest results on intensity distribution transformation from Gaussian to a flattop and doughnut are presented in the paper. The wavefront was modified with bimorph deformable mirror to reach the desired intensity distribution in the farfield. LC phase modulator was also considered as an alternative device for laser beam shaping. The theoretical calculations and experimental results of the efficiency of different types of wavefront correctors are given.

Laser beam focusing through the atmosphere aerosol

Distortions of the scattered laser beam (λ=0.65μm) were numerically estimated by means of Shack-Hartmann technique and experimentally measured. The ability to focus laser beam, passed through the scattering suspension of polystyrene microspheres in distilled water, using bimorph deformable mirror was investigated both numerically and experimentally. Shack-Hartmann technique was used to measure the local slopes of the Poynting vector, and CCD camera was used to analyze the intensity distribution of the focal spot in the far-field. Bimorph deformable mirror with 14 electrodes was utilized in order to increase the focusing efficiency of the laser beam. The voltages to be applied to the mirror electrodes were calculated using three techniques: LSQ (least squares) fit-error minimization by Shack-Hartmann sensor, Hillclimbing optimization by Shack-Hartmann sensor and Hill-climbing optimization by the far-field CCD camera.

The use of modified hill-climbing algorithm for laser beam focusing through the turbid medium

We investigate the ability to focus the laser beam (λ=0.65μm) propagated through the scattering suspension of polystyrene microspheres in distilled water by means of bimorph deformable mirror. Shack-Hartmann sensor was used to measure the local slopes of the Poynting vector, while the CCD camera was used to measure the intensity of the focal spot in the farfield. Bimorph deformable mirror with 14 electrodes was applied in order to increase the intensity of the focal spot in the far-field. We investigated the efficiency of the laser beam focusing improvement by means of three techniques: LSQ fiterror minimization by Shack-Hartmann sensor, Hill-climbing optimization by Shack-Hartmann sensor and Hill-climbing optimization by far-field CCD camera.

Laser beam focusing through the scattering medium by means of adaptive optics

Laser beam propagation through the scattering suspension of polystyrene microspheres in distilled water was studied. The distorted laser beam was analyzed by both Shack-Hartmann sensor and CCD camera. The measured local slopes of the Poynting vector were compensated for by means of bimorph deformable mirror with 14 electrodes in order to increase the intensity of the focal spot in the far-field. Three different techniques for laser beam focusing were implemented and compared: LSQ fit-error minimization by Shack-Hartmann sensor, Hill-climbing optimization by Shack-Hartmann sensor and Hill-climbing optimization by far-field CCD camera.