电子束辐照对BBO晶体一阶超极化率的影响

摘要

与传统热力学方法不同,本文从辐照电场角度出发研究电子束辐照对BBO（β-BaB2O4）材料的非线性性能影响。利用量子化学方法和有限场方法计算其一阶超极化率β的全部分量,以此分析不同辐照强度下β的改变规律。研究表明：在电子束流强度为50μA的情况下,当射线能量小于400Mev时辐照电场对β的影响不大,平均值βav波动幅度最大仅为3%;此后随射线能量增大βav开始急剧下降,能量越高下降速度越快,420Mev时已经下降10%,材料面临失效的危险。研究结果还表明辐照电场对β三个分量的影响并不一致,随辐照能量增加βx、βy分量呈减小趋势,但βz分量却增加较快,预示着晶体中的共扼π轨道可能受到破坏。%We researched the mechanism not based on the traditional thermodynamics effect but on the microscopic origin of nonlinear effect for the fully consideration of the correlation of the e-beam irradiation electro-field and the properties of nonlinear material BBO（β-BaB2O4）.By resorting to quantum chemical methods and finite field method the first-order hyperpolarizability β was calculated.According to the results we analyzed the influence of different irradiation conditions on the nonlinear coefficient of BBO crystals.The results show that when the energy of electron beam is less than 400Mev with the current of 50μA,βav basically remains unchanged and the largest fluctuation is only 3%.But after this,βav begins to decline sharply.The higher the energy is,the faster the decline is.When the energy is 420Mev,βav decreases 10%,and the material has a trend of being damaged.The results also show that the influence of the irradiation electric field on the three components is not uniform.With the increase of irradiation energy,x and y components show a decreasing trend,but z component increases rapidly,indicating that the π-conjugated orbits may have been destroyed.