3¦Ø Optics System Beam Quality Change Characteristics Of The Icf Driver

Beam quality control is the most important segment in high power solid state laser facility construction,for the mean requirement of precise physics experiment and the operation safety of laser facility in high capacity.The 3ωoptics system which converts the 1ωbeams to the third harmonic and focuses them onto the target is an important segment of beam quality degradation.This dissertation studied the basic rules of beam transfer in 3ωoptics system for qualify the optics specifications and 1ωbeam quality before frequency converter.The main research topics included;1.The background and content of beam quality control for high power solid state laser facility were summarized,the influencing factors and research status of 3ωbeam quality were elaborated from too aspects;frequency conversion and 3ωbeam propagation.2.Perturbation theory of beam aberrations during frequency conversion was studied, and influence of 1ωamplitude and phase modulation,non-uniformities of KDP crystal refractive index on 3ωnear-field distribution was investigated.3.Relations between 3ωfar-field and 1ωphase ripples were analyzed,and effects ofΣB_1ωon 3ωfar-field were also studied.Comparison of measured 3ωfar-field was conducted between two beams of SGⅢprototype facility; results were in accordance with the theoretical analysis.4.Based on the B-T theory,increase of beam modulation during 3ωoptics was derived under the condition of nonlinear propagation; by the medium-high phase peeps constructed according to the surface shape of typical KDP crystals,influence ofΣB_3ωon beam near-field quality was investigated.