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Design And Application Studies On The Curvature Sensor With A Grating

Posted on:2009-07-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:F J XiFull Text:PDF
GTID:1118360278956592Subject:Optical Engineering
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The wave-front curvature sensor with a defocus grating developed in recent years has a promising prospect in fields of optical metrology, laser diagnose, vision science, and directed energy technique, which attributes to the advantages of its fully optical measurement and no vibrating components. In this dissertation, the theoretical analysis, design methods and practical applications of the curvature sensor with a grating are addressed.In the theoretical analysis, differing from traditional methods of geometrical optics, the transfer function approach is employed in the frequency analysis of the curvature sensing technique. The analytical expression of the optimum propagation distance is proposed as one quarter of the Talbot length at the critical frequency. The comb filter model of a curvature sensor is established, according to which the concept and the design method of dual-z or multi-z curvature sensing is presented.Owing to the limitations of the amplitude defocus grating, the phase profile and diffraction properties of the phase defocus grating are analyzed with the Fourier optics approach, in which the binary phase profile of the grating is determined and its transfer function and diffractive efficiency are estimated. Also, the chromatic dispersion of the grating is analyzed. Based on the design, the prototype of the curvature sensor with a phase grating is fabricated. The experimental results show that the diffractive efficiencies in the±1 diffraction orders of the designed phase defocus grating measure up to 38.1% and 40.4% respectively, which can increase the light availability of the wave-front curvature sensor and will be especially applicable to the detection and the compensation of weak photosignals in adaptive optics systems.In the wave-front measurement, the curvature signal induced by the turbulence phase screen is numerically simulated and reconstructed with the GS algorithm and the Green's function algorithm respectively. At the same time, the convergence and pattern aliasing of these two algorithms are analyzed. The wave-front aberrations of the liquid laser gaining medium are measured using the constructed curvature sensor with a grating, reconstructed with the Green's function algorithm. The experiment results indicate that the above mentioned curvature sensor is suitable for several aperture geometries and verify the validity of theoretical analysis and design methods of the curvature sensor with a phase grating.Based on the above researches, two important applications of the curvature sensor with a grating in the laser field are further explored. Firstly, the measurements of thermal lens effects in the high energy solid heat capacity laser and the side-pumped Nd:YAG laser are realized using the curvature sensor with a grating. Secondly, aiming at the demands of the M~2factor measurement, design methods and structure demands of two crossed defocus gratings in the measurement system are analyzed. The M~2factor measurement system with crossed defocus gratings for the laser at 1064nm is developed and the M~2factors of the 1064nm Nd:YAG pulse laser are measured. The experiments demonstrate that the M~2factor measurement system comprised of crossed defocus gratings has the predominance of measuring the pulse-to-pulse or varying M~2factors.
Keywords/Search Tags:Adaptive optics, wave-front curvature sensor, transfer function approach, Talbot effect, comb filter model, defocus grating, Fresnel zone plate, GS algorithm, Green's function algorithm, thermal lens effect, M~2factor
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