一种潜在的新型非线性光学材料-氟硼酸铍

氟硼酸铍（Be2（BO3）F,简写为BBF）,属单斜晶系,空间群为C2。该化合物含有BO3平面三角形基团。BeO3F四面体与BO3基团连接形成六元环,通过Be—F—Be将层与层之间交叉联结起来。理论计算表明其Eg=7．80eV,吸收边在150nm;有较大的双折射率,△n=0．0915;倍频系数计算结果显示：d22=-0．0723pm／v,d16=-0．0172pm／v,d14=-0．00928pm／v,d23=0．0053pm／v。对合成得到的材料粉末样品进行XDR物相测试验证和热分析。粉末倍频测试表明该材料的倍频讯号强度为KDP的1／4左右。实验证明BBF可能是一种潜在的紫外、深紫外非线性光学材料。     

Linearity of quadrant avalanche photodiode in laser tracking system

The tracking precision of laser tracking system is affected by the angular resolution of quadrant avalanche photodiode. According to the detecting principle of quadrant avalanche photodiode, the light spot area, the optical intensity distribution, the non-uniformity of response, and the signal-to-noise ratio （SNR） that affect the linearity of the detector are studied. The light optical spot area and the optical intensity distribution can be adjusted through software. The non-uniformity of response and the SNR are influenced by the noise of the detector. Because the noise is affected by the optical intensity of the incident laser, it is difficult to obtain the law of the linearity caused by noise. When the light spot area and the optical intensity distribution are fixed, the other factors can be measured. With the detector scanned in raster scanning mode, the non-uniformity of response is measured at different SNRs. The linearity of detector is measured by a moving target that can reflect the illuminating laser to the detector in diffuse reflection mode. The nonlinear error of the linearity of detector can be minimized by increasing the SNR.