Since the jitter frequency of incident laser beam becomes higher in the ‘Common Path/Common Mode’ (CP/CM) system due to the guiding system added to the laser module, the current laser-beam stabilizing control with hartmannshack sensor is not enough. As we all know, better beam stabilizing control effect requires higher detecting frequency. Generally, the detecting frequency of hartmann-shack sensor in the CP/CM system is far lower than the far-field spot. So we want to use the far-field spot of the SARA to feedback instead of the hartmann-shack sensor. In this work, we study the far-field spot of a 61-unit SARA from the CP/CM system. We ratiocinate the process of the simulation based on Fresnel diffraction and Fourier optics. Comparison between standard far-field spot and the far-field spot from sixty one units SARA based on duty ratio of the retro reflectors and different wavefront tilts aberrations is given, while the wavefront is given in zernike model.
Laser Guide Star (LGS) is an artificial atmospheric turbulence probing source of adaptive optics (AO) for compensating for the wave-front error of interested object in real time, and for providing approximate diffraction-limited resolution recovery. Actually the unavoidable anisoplanatic error resulting from different light experience between the LGS and the object of interest through turbulent atmosphere will lead to an incomplete wave-front distortion compensation of the object. In this paper the statistics of anisoplanatic errors and their associated Zernike-modal variances have been systematically investigated for different LGS sources by means of numerical simulation, including Rayleigh LGS and Sodium LGS. The numerical results show that the probed wave-front expanded Zernike-modal decorrelation versus angular deviation between the LGS and the object of interest becomes much more sensitive for the higher altitude LGS. For minor angular deviations with LGS focal spots being still within the ray path from the object to the telescope, the reduction of the error from turbulence above the LGS altitude is still a leading cause to decrease the residual error variance after AO correction. However, for the greater angular deviations with LGS focal spots moving on the outside of the ray path from the object to the telescope, higher-altitude LGS could lead to an increasing residual error variance after AO complete correction with its wave-front as reference. At this point the adopted LGS operation mode and the AO system modal correction optimization should be taken into account for achieving a desired residual wave-front error.
A conventional adaptive optical system (AOS) often measures the wavefront slope or curvature straightly by a wavefront sensor. However, another alternative approach allows the design of an AOS without an independent wavefront sensor. This technique detect the image quality affected by phase aberration in laser wavefront rather than measuring the phase aberration itself, and then the image quality is taken as a sharpness metric. When wavefront phase aberration is corrected, the sharpness metric reaches its maximum value. In this paper, a wavefront sensorless adaptive optical system (AOS) has been set up. This system mainly consists of a 19-element piezoelectricity deformable mirror (DM), a high voltage amplifier, a set of 650nm laser, a CCD camera and an industrial computer. The CCD camera is used to measure the light intensity within an aperture of the focus plane, and then this intensity is regarded as the sharpness metric to optimize. A Modified Hill Climbing Algorithm (MHC) and a Genetic Algorithm (GA) are used to control the DM to correct the phase aberrations in this system. Experimental results show that both of these two algorithms can be used successfully in this indirect wavefront measurement AOS. However, the GA can obtain better performance than the MHC. After phase aberrations are corrected, the βfactor are reduced from 5.5 to 1.5 and 1.9, from 30 to 1.2 and 1.4 respectively.
For some adaptive optics (AO) systems, one deformable mirror (DM) can not meet the need of large stroke and high
spatial frequency. In this paper, a double DMs way is present. In this system, a large stroke DM (LSDM) with low
spatial frequency corrects low order aberrations and a high spatial frequency DM (HSFDM) with small stroke corrects
high order aberrations. The decoupling algorithm of two DMs is essential for working properly. In this paper, a
decoupling algorithm and experimental results for a double DM AO system are presented. The result indicates that the
compensation result of double DMs AO system is almost the same as that of the conventional AO system using single
DM with ideal stroke and equivalent spatial frequency.
Intracavity adaptive optics has been successfully used in solid state lasers to improve output laser beam quality. However, In order to utilize this technology to improve the output laser beam quality successfully, the distribution characteristics of phase aberration in the laser resonator should firstly be known. Thus, a set of Hartmann- Shack wave front sensor (HSWFS) to measure the time and space characteristics of phase aberration in a diode-side-pumped Nd:YAG laser was set up. In this paper, the HSWFS is briefly introduced. The experimental results for measurement of the phase aberration in a diode side-pumped Nd:YAG laser are presented. The experimental results show that, the main phase aberration in the resonator is generated by the Nd:YAG rod. The phase aberration induced by thermal deformation in the cavity mirrors is minor. The temporal behavior of phase aberration in the resonator and from cavity mirrors under light heating was also obtained.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.