The Full Compensation Of Beam Near-field Amplitude And Phase Fluctuations In Adaptive Optics Control Technology

Adaptive optics (AO) is a real-time measurement and aberration correction technology, which applies to compensating the aberration of beam when it propagating the atmospherc turbulence. Traditional adaptive optics is to use a single deformable mirror (DM) compensation for the beam phase distortion. The more effective compensation is correcting the amplitude and phase distortion synchronously. A proposed method to compensate for amplitude and phase distortion is the use of two DMs. In this paper, we study the AO theory and use the existing DM devices to design the two DMs AO system. This system can compensate the distortion of amplitude and phase for beam. In the experiment we achieve this full compensation technology. The principles, the characters and application prospect of the two DMs AO system are studied by theoretic analysis and experimental verification.This paper is devoted to the principles of two DMs AO system, using of phase-type liquid crystal spatial light modulator (LC-SLM) as a DM. Accordance with correction near-field intensity of beam, validation of DMs AO system in experiment and realization of the closed-loop experiment to conduct the feasibility of full compensation in two DMs AO system.First, the AO system to compensate for laser system application is introduced. The simulation of tranditional single DM AO system compensating phase distortion is analyzed. Result shows that the only pahse compensation can not make the beam distortion fully corrected, especially when the beam propagation is so distance, out of radio aperture is so small and the atmospheric disturbance is so strong. According to the two DMs AO theory, the beam amplitude and phase distortion is corrected at the same time. Simulation results show that laser beams through the full compensation, the quality of laser beam in the near field intensity is improved and the far field image is close to diffraction limit.Second, in the two DMs AO system, the intensity and phase of the beacon beam reaching the transmitting system can be detected by the detectors, and then the measured results are used to control two DMs. The key technique is to determine the required phase of DM1, thus the near-field intensity of beam is corrected. The phase-iterative algorithm based on the traditional algorithm G-S algorithm is presented. This algorithm is using the emitted laser known amplitude distribution and the near-field receiving plane needed amplitude distribution to iterate the phase of beam. We can control the DM to give the beam this pahse, so that the beam near-field distribution is close to the requirements of the ideal field distribution, so as to achieve the control of near-field intensity of the beam. The AO system based on G-S algorithm to control the near-field intensity of the beam is designed for the first time, and experiments with good results.Again, in the full compensation theory, when the laser reaching the second DM, the amplitude distribution is according to beacon and phase conjugation. In optical reversion and phase conjugation principle, the primary laser to target the field distribution will beacon unanimously. According to the principle of optical reversion and phase conjugation, the method based on AO technology to control beam near-field intensity is proposed, and the first experimental study is carried out. Simulation and experimental results show that the system can realize the control of near-field intensity, so that the beam quality is improved. The experimental system verifies the feasibility of the two DMs AO system to improve the near-field intensity of beam for the first time.In addition, a schematic experiment of the two DMs AO system is designed to verify the ability of full compensation. In experiment has no beacon, but from the available aberration plate information we can calculate the required deformation of twoDMs.The ability of compensation between two DMs and single DM is compareted, showing the advantage of full compensation using two DMs for adaptive optics wavefront correction.Finally, based on the theory of full compensation using two DMs, we design a set of two DMs AO closed-loop system for the first time. The intensity and phase of the beacon beam can be detected by the detectors, and then the measured results are used to control two DMs. We can use CCD to detect the amplitude distortion and iterate the required phase for DM1, use Hartmann sensor to detect the phase distortion and control DM2. The system can correct the distortion of phase and amplitude at the same time in closed-loop control. Simulation and experimental results show that, through the first set of two DMs AO system the fully compensation is effective. The quality of laser beam in the near field is improved and the far field image is close to diffraction limit in the experiment. This dissertation will provide some reference and experience for the two DMs AO system in practical application.