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We present the results of the aberration correction of laser radiation wavefront using a dynamic method for determining the reference wavefront. The method, which is based on the processing of synchronously obtained data on the near- and far-field zones, significantly improves the focusing quality with active wavefront correction, especially under conditions of dynamic aberrations. An increase in the Strehl number S from 0.7 to 0.86 is demonstrated when a beam 18 cm in diameter is focused by an F/2.5 parabolic mirror.

The results of the operation of a wavefront correction system based on a deformable bimorph mirror of the PEARL subpetawatt laser facility are presented. An improvement in the quality of focusing of laser radiation, which led to an increase in the Strehl ratio from 0.3 to 0.6, is demonstrated. The features of the compensation for phase distortions of the wavefront in the case of a low pulse repetition rate, as well as the correct allowance for the noise of the CCD camera when calculating the Strehl ratio are investigated.

—A wavefront corrector has been designed in the form of a cooled stacked-actuator deformable mirror for the correction of aberrations of laser radiation propagating through the turbulent atmosphere. The main parameters of this mirror are theoretically estimated. A technique for cooling the reflecting surface of the wavefront corrector through piezo actuators is suggested and experimentally tested. The main parameters of the deformable mirror are measured: the initial shape of the surface, the response functions of the actuators, the mirror stroke, and the frequency-amplitude characteristic of optical surface.

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.

Deformable mirrors in adaptive system for high power lasers should have high damage threshold and thermally stabilized surface. The cooling is required for average beam power above 100W. In this paper, the problem of the thermo-stabilizing of the deformable mirrors is studied. Bimorph deformable mirrors (BDM) and stack actuator deformable mirrors (SADM) are considered. For BDMs the active and passive cooling designs have been implemented. In active design, the waffletype cooling system for circulation of the cooling liquid was made inside of the thin substrate. In passive design, the periphery surface is thermally contacted with the condenser which temperature is constant. Such BDMs not damaged at CW power density 20kW/cm2 when the beam fills full surface of the mirror and can be used in powerful solid state ceramic YAG lasers. SADM is most suitable to correct for small-scale and high-speed aberrations. We developed SADM where reflecting substrate is cooled through the actuator bodies. Individual actuators are housed in metal holders and can be replaced if they fail due to electrical breakdown. SADM has the diameter 120 mm and included 121 actuators. The deformation stroke of the actuator was 7μ. The first resonant frequency was 18.5 kHz, which allowed operating in adaptive system in kHz range.

Adaptive system for wavefront correction based on 240-mm bimorph deformable mirror and Shack-Hartmann wavefront sensor is presented. The dynamic characteristics of the deformable mirror and the performance of the wavefront correction in various operating modes of the PEARL facility as well as the features of phase distortion compensation in a single-shot generation regime are studied. An improvement in the quality of focusing that led to an increase in the Strehl ratio to 0.6 is demonstrated.

Stacked-array deformable mirror is one of the most popular tools for correction of wavefront aberrations. We manufactured the stacked-array deformable mirror with small diameter by using piezoceramic combs with few actuators on them. In this case the aperture of mirror will be equal to 30 mm. The stroke of such mirror would be about 5 microns. The thickness of the mirror substrate is 1 mm. Developed deformable mirrors will be suitable for fast adaptive optical systems for optical radiation transferring through turbulent atmosphere tasks.

The article discusses the use of stacked-actuator adaptive mirrors to improve the focusing of laser radiation. The criterion of focusing efficiency is the fraction of the energy of the laser radiation passing through the pinhole located in the focal plane of the focusing lens.

Fast adaptive optical system usually used in atmosphere tasks—for wavefront correction of the laser beam passed through a turbulent atmosphere. As a rule, the frequency of waveform distortions is about 100 Hz (roughly). Consequently, the frequency of discreet system should be about 1500 frames per second. Achieving such performance is possible by FPGA using for full closed-loop cycle: image receiving from wavefront sensor, voltages array for deformable mirror calculation the and provision fast applying these voltages to deformable mirror. Main aspects of FPGA using to minimize the whole cycle of adaptive optical system are considered.

One of the main problems in tasks of laser beam propagation though Earth’s atmosphere is decrease the efficiency of the optic-electronic systems operation due to atmospheric turbulence influence that leads to laser beam’s wavefront distortions. Use of fast adaptive optical system are suggested to solve this problem. It allows to compensate the wavefront distortions, which upper bound of the spectrum is up to 150 Hz, in real time. Owing to the fact that adaptive optical system is discrete (it’s defined by digital camera included in the system), the sampling rate shall be at least 1500 Hz (frames per second).

Bimorph deformable mirror for correction of low-order aberrations of laser radiation was manufactured. Two technologies were used to develop this wavefront corrector: laser engraving technology and ultrasonic welding technology. The mirror has aperture of 10 mm and 13 control electrodes. The thickness of the wavefront corrector is 1 mm. The applied voltages took values in the range from -150 to +200 V. The stroke of the mirror for one electrode was equal to 1 micron (P-V). The first resonant frequency was found at 10.8 kHz. Such mirror can be used in closed-loop adaptive optical system with speed about 1.1 kHz.

The development of laser technique and various applications of laser radiation requires the use of devices that can modify as well as correct for the wavefront of laser beams. In these cases, the use of deformable mirrors is simply very important. In the high-power laser setups, the task of correction of laser aberrations assumes the use of thermally stabilized optical elements. We consider that two types of wavefront correctors are the most well-suitable for such an application: bimorph deformable mirrors and stacked-actuator (SADM) ones. Bimorph deformable mirrors proved their reliability and could be used in high-power industrial lasers. They can perfectly correct for low-order and are simple in manufacturing. On the contrary stacked-actuator mirror can reproduce high-order wavefront aberrations and thus have high spatial resolution of control elements and might be applied in fast adaptive optical systems to correct for laser radiation distributed through turbulent media.

Many atmospheric applications based on the laser beam passed through the Earth’s atmosphere are exposed the distortion of the laser beam wavefront, which ultimately leads to a decrease in their efficiency. Such tasks include the transmission of powerful laser radiation over a distance (recharging batteries of drones and low-orbit satellites, delivering energy to hard-to-reach places, destroying fragments of space debris in low orbits), creating protected optical communication lines, increasing the resolution of telescopes, etc. One of the methods to improve the efficiency of such systems is the use of adaptive optics methods and tools that allow the wavefront correction in real time. The features of constructing such a system using FPGA as the main control element are considered.

Stacked-actuator deformable mirrors (SADM) allow to compensate for wide range of wavefront distortions. They are distinguished for their large stroke of control elements, high operational speed, the possibility of correction for small-scale aberrations. The SADM with 6x6 actuators placed on the aperture 30x30 mm was developed. The thickness of mirror substrate was 1 mm. The maximal deformation stroke of the SADM was about 5 microns.

Bimorph deformable mirror with 63 electrodes on 20 mm aperture is discussed. Methods of dividing all round electrode into sectors with a square of 2-4 mm2 are described. Results of flat-top beam formation by means of 50 mm bimorph deformable mirror with 48 electrodes and 20 mm miniature bimorph mirror with 27 electrodes are presented.

An adaptive optical system that implements a phase conjugation algorithm designed to compensate for the effect of atmospheric turbulence the propagating laser beam is presented. The system allows compensating for the influence of atmospheric disturbances up to 200 Hz (in terms of sine). To achieve the compensation effect system operates at a frequency of 2000 Hz (in terms of fps - frames per second). Such high performance can be achieved only when using FPGA as the master control element of the system. The results of correction of disturbances obtained by using a heat fan, simulating the turbulence to frequencies of 200 Hz, are presented.

Laser beam shaping technology nowadays requires as small diameter of the adaptive optics as possible. In our lab we usually control for laser radiation by means of bimorph deformable mirrors with a typical size of more than 50 mm. To fit the most of industrial and scientific applications the aperture of the corrector should be reduced because the use of extra optics instead makes the whole optical scheme more complicated and introduces extra distortions. But in a bid to reduce the size of the mirror we should care of the response of the mirror electrodes which obviously should not decrease drastically. Here we present 20 mm bimorph mirror with high density of electrodes which is manufactured using laser engraving technology to divide the electrode on the piezoceramic disc into a large number of the controlled sectors. The ability of laser beam formation by means of this mirror is discussed, the results are compared with the ones obtained using 50 mm bimorph deformable mirror.

As well known, the quality of radiation of laser beam is reduced during propagation along optical trace, because of various reasons (for example, atmospheric turbulence, scattering, thermal fluctuations etc.). We propose small-size deformable mirrors with high spatial resolution of control elements, that will allow to compensate for wavefront aberrations in wide range. Developed wavefront corrector could be used in different scientific areas: free-space communications, destruction of space debris, etc.

In tasks related to free-space communications, a significant role has a turbulent atmosphere which influences lead to a decrease in the efficiency of systems. Since the characteristic turbulence spectrum rarely exceeds 100 Hz for typical paths, it is proposed to use a discrete adaptive optical system with a frequency of 1500 frames per second to reduce the influence of the atmosphere. The structure of the system based on the use of FPGA as a computing device as well as the main results associated with the correction of both static and dynamic components of aberrations are presented.

The article discusses the use of stacked-actuator adaptive mirrors to improve the focusing of laser radiation. The criterion of focusing efficiency is the fraction of the energy of the laser radiation passing through the pinhole located in the focal plane of the focusing lens.

To correct for phase distortions in high-power laser setups a stacked-actuator deformable mirror with water cooling was developed. The main characteristics of the mirror such as the initial surface profile, response functions of the actuators, maximal stroke and amplitude frequency characteristic were shown. The quality of initial surface was equal to 0.14 µm (P-V). The maximal stroke of the mirror was about 7 µm. The first resonant frequency was found at 18.5 kHz, that would allow to exploit such wavefront corrector in high-speed adaptive optical systems. The measured hysteresis of the deformable mirror was equal to 12%. Experimental investigations of proposed cooling method of the mirror surface through actuators were performed.

Deformable mirrors are vital components of any adaptive optical system. Considering such a crucial role in compensation of incident wavefront distortions, the main requirements are imposed on these elements that determine performance of the entire system. To correct for phase distortions in high-power laser complexes a stacked-actuator deformable mirror with water cooling was developed. The main characteristics of the mirror, such as the initial surface profile (flatness), response functions of the actuators, maximal stroke, and amplitude-frequency characteristics are presented in this paper. Experimental investigations of the proposed cooling method of the mirror surface through actuators were performed.

The most important part of any adaptive optical system is a deformable mirror. One of the most widely used type of such mirrors are the bimorph ones. In fact, there is no problem to manufacture a wide aperture bimorph wavefront correctors that perfectly can compensate low-order laser aberrations. But if one needs a tiny deformable mirror to correct for high order aberrations with reasonable amplitude, he usually will use stacked actuator mirror or a MEMS one. In this presentation we suggest the new design and technology of production of a small size bimorph mirrors to be used to correct for atmospheric phase fluctuations. Our mirror has the diameter of 30 mm and 37 control electrodes (mirror with 20 mm and 63 control electrodes is being developed). The resonance frequency of 13.2 kHz is due to its small diameter. At the same time, large number of electrodes allows to reproduce high order aberrations. To manufacture this device two modern technologies are used: ultrasonic welding and laser engraving technology.

In this work, we investigate the efficiency of the use of the bimorph deformable mirror to focusing laser beam in the pinhole. Pinholes of different diameters are used as an instrument for focusing verification. Different algorithms are discussed and analyzed for the investigation of the process of the beam focusing. It is shown that tip-tilt correction is an essential condition for increasing the focusing efficiency.

High-power laser systems are widely used for technological purposes or laser fusion experiments, but also to deliver the energy to some remote places here on the Earth as well as in space. Probably the only instrument to improve the phase structure of the laser beam is to use methods and elements of adaptive optics. The heart of any adaptive optical system is of course the deformable mirror. That is why the research and development of such optical elements continues for many years already. Here we propose a new stacked actuator mirror to be used to correct for not just the turbulent phase fluctuations, but also it should work with high CW power laser beams. Therefore, our mirror is a water-cooled one. Another important feature of this device is that each actuator could be easily substituted in case of failure. The mirror is 120 mm in diameter and has 121 control elements. Main characteristics of a mirror are presented in this work.

The article discusses the use of bimorph adaptive mirrors to improve the focusing of laser radiation. The criterion of focusing efficiency is the fraction of the energy of the laser radiation passing through the pinhole located in the focal plane of the focusing lens.

To compensate for the wavefront distortions in high-power laser setups we developed stacked-actuator deformable mirror with aperture of 120 mm and 121 control actuators and bimorph deformable mirror with size of 410x468 mm. Design of the stacked-actuator mirror provides substitution of broken piezoactuators. Also, we can provide thermostabilization of the mirror surface through actuator body. Bimorph mirror has high surface amplitude deformation (about 20 um) and good flatness of the initial surface of the mirror (0.03 um RMS). Also, there is a possibility of preliminary adjustment by the piezostacks, which situated on the edge of the mirror.

As it is well-known, the laser radiation, propagated through different mediums, is affected by wavefront distortions and thus the quality of the radiation is significantly decreased. To compensate for the wavefront aberrations adaptive optics means are used. We developed miniature bimorph mirror with 37 electrodes. To manufacture this type of mirrors two technologies were used. Those are laser engraving technology for drawing electrode grid on the piezoceramic disc, and ultrasonic welding technology to connect wires to the control electrodes. Main parameters of such a deformable mirror were investigated and presented in this paper.

Focusing laser beam through a pinhole by adaptive optics is investigated as an approach to the optimization of a fiber-coupled entangled photon source. Efficiencies comparable with the diffraction limited ones are obtained.

Fast adaptive optical system can be used, for example, for correction of laser beam passed through a strong turbulent atmosphere. The frequency that such a system should operate with to achieve an acceptable level of wavefront correction is about 1 - 1.5 kHz. There are two most popular methods to develop this system: by using a standard PC computer and by using FPGA. This paper presents the advantages and disadvantages of each of these approaches. The results obtained with the use of these systems are presented. Recommendation for achieving higher performance are given.

During propagation of the high-power laser radiation through atmosphere the quality of the beam is significantly reduced due to atmosphere turbulence. For compensation of the wavefront distortions and improving quality of radiation, as a rule, adaptive optics approaches are used. The design and main characteristics of 121-element water-cooled stacked-actuator deformable mirror for this kind of applications is discussed in this paper.

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.

conventional high-power lasers suffer from the wavefront aberrations, that significantly decrease the radiation power during the employment of the laser complex. For compensation of the wavefront distortions and improving the quality metrics of the radiation adaptive optics approaches are used. The 121-elements and the 19-elements stacked-actuator deformable mirrors for these kind of applications were developed.

semipassive bimorph flexible mirrors is one of the most widely used devices for correction of the given laser beam intensity. However, the key disadvantage of these kind of mirrors is their low spatial resolution of the corrected phase. In this work, we present two approaches for increasing spatial resolution of the deformable mirrors – one to use a multilayer bimorph mirrors and another to put higher density of control electrodes and use ultrasonic welding to make the wire connection to these electrodes.

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.

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 and correction of the given laser beam intensity and phase is an important practical and scientific problem. Semipassive bimorph flexible mirror is one of the most widely used devices for this purpose. But the key disadvantage of these kind of mirrors is their low spatial resolution of the corrected phase. Mainly this problem occurs when one deals with the small aperture wavefront correctors. In this work we present two approaches to overcome this problem – one to use a multilayer bimorph (multimorph) mirrors and another to put higher density of control electrodes and use a special technique (ultrasonic welding) to make the wire connection to these electrodes. Here we also present a numerical model to simulate bimorph correctors, based on a variation approach of the finite elements method.

A rapid adaptive system for atmospheric turbulence compensation is considered in the work. It operates with a frequency of 200 Hz. A deformable mirror with 97 piezoactuators as a stacked actuator and a 2-kHz Shack-Hartmann wavefront sensor have been used for the adaptive system design. A dependence of the residual error of a sine signal correction on the speed of system response is also considered.

Key elements of the fast adaptive optical system (AOS), having correction frequency of 1400 Hz, for atmospheric turbulence compensation, are described in this paper. A water-cooled bimorph deformable mirror with 46 electrodes, as well as stacked actuator deformable mirror with 81 piezoactuators and 2000 Hz Shack-Hartmann wavefront sensor were considered to be used to control the light beam. The parameters of the turbulence at the 1.2 km path of the light propagation were measured and analyzed. The key parameters for such an adaptive system were worked out.