Diffractive Optical Element And Uniform Illumination System Design And Analysis Of Experiments In ICF

In laser-driven inertial confinement fusion (ICF), require high-power laser to achieve the target surface flattened, the steep side, low sidelobe uniform lighting. At home and abroad, optical smoothing of the program is Continuous Phase plate (CPP), smoothing by spectral dispersion (SSD) and orthogonal polarization smoothing (PS:Polarization Smoothing, birefringent crystal optical wedge) multi-beam superposition and other methods combined, and constantly improving the CPP design performance, increase of the wave-front distortion tolerance, to optimize the selection of SSD parameters to better target surface illumination uniformity performance.In this paper, the main research work at the support of the national high-tech research and development plan (Plan 863) significant special issue (863-804) "for use in inertial confinement fusion of the large size of diffractive optical element design and manufacture" and the subsequent "target surface laser-smoothing technology" fund for the engineering study. Research on "the ICF DOE and uniform illumination system design" themes, consists of three main parts :The first part, the large size of diffractive optical element was design for uniform illumination. In the second chapter, has systemically summarized the current direct design method of diffractive optical elements (DOE), including iterative algorithm, optimization algorithms and a combination of both hybrid algorithm. And given the spot-evaluation of the quality standards, In the following chapters further introduction of the power spectral density of the optical field evaluation. In chapter III major analyses large size and complex ShenGuang system, a variety of horizontal alignment, beam and the beam size jitter control difficulties, analysis of large size DOE horizontal position error tolerance. Analyses of the practical application of the incident light was different from the design of the incident light in caliber and shape, uniform illumination changes and the performance of sub-units symmetry, reveal the existing block design in the application of the DOE's deficiencies. An improved subregional DOE indirect method was proposed. This algorithm is divided into two steps, first using iterative algorithm design DOE constant illuminating region. The second step search algorithm design with the remaining regions. This method can be designed in the preset lighting caliber, they will maintain higher smoothing properties of the DOE, equivalent to the design phase of the DOE on improving the lighting caliber tolerance and anti - horizontal position error capacity.The second part, SSD and the DOE were jointed. With the depth of research and domestic manufacturing maturity ShenGuang devices intensity smoothing system was expand to the time domain using the SSD system. Because it is a first attempt, work was begun from the principle of SSD. 1D SSD and DOE to find optimal selection of the key parameters of the SSD, given to the beam smoothing SSD parameters. SSD will then be extended to two-dimensional simulation. Comparison and integrated simulation and modeling at the speed of the two methods on the merits, To hours as a method of modeling simulation methods. The simulation is considered a sampling interval of refinement, SSD discussed under the spot position to offset the non-sampling intensity shifted effect. Subsequent theoretical analysis and simulation experiments closely with the scene. Proved divergent spherical wave incident does not affect SSD and the DOE Joint smoothing properties. SSD for the experimental data offline done a detailed analysis, In contrast to beam smoothing SSD system using the spot before and after the change, confirms the theory and simulation of high frequency predicted decreased by speckle suppression.The third part, the introduction of turbulence on the laser transmission disturbance achieves the temporal spot smoothing. Turbulent air mass will make the wave before the introduction of light intensity smoothing system to replace the multi-dimensional function of SSD. Turbulence theoretical description of the wave and the spread of other areas, workers have been detailed studies, we borrow other areas of turbulence statistical description. But in most areas of applications need to avoid the turbulence of wave propagation effects here get a positive use. The arriving angle ups and downs was analysis for it important influences the light smoothing. Main focus on the means of numerical simulation, the simulation method is the phase screen method. To be included in the large-scale turbulence effect, the sub-harmonic phase screen selected. Built the system model and numerical simulation platform, set specific parameters, on the whole turbulent wave propagation and after MPP and the focusing lens convergence characteristics done a detailed simulation and analysis. Finally, the method in turbulent beam smoothing of a preliminary experiment was suppressed by high-frequency components of the spot, numerical simulation and analysis of the conclusions are consistent.