沉积温度对热舟蒸发MgF2薄膜性能的影响

采用热舟蒸发方法沉积了氟化镁（MgF2）材料的单层膜，沉积温度从200℃上升到350℃，间隔为50℃。测量了样品的透射率和反射率光谱曲线，进行了表面粗糙度的标定，并在此基础上进行了光学损耗及散射损耗的计算。同时对355nm波长处的激光诱导损伤阈值进行了测量。结果表明：随着沉积温度的升高，光学损耗增加;在短波长范围散射损耗在光学损耗中所占比例很小，光学损耗的增加主要由吸收损耗引起；在355nm波长处的损伤阈值变化与吸收损耗的变化趋势相关，损伤机制主要是吸收起主导作用。样品的微缺陷密度也是影响损伤阈值的一个重要因素，损伤阈值随缺陷密度的增加而降低。

Single layers of MgF<inf>2</inf> were deposited upon super polished fused-silica substrates by resistance boat evaporation at different temperatures from 200°C to 350°C by increasing step of 50°C. The transmittance and reflectance spectra were measured and the root-mean-square surface roughness was determined. The total optical loss and scattering loss were calculated. The laser-induced damage threshold(LIDT) was characterized at the wavelength of 355 nm for certain samples. It was found that the total optical loss and the root-mean-square surface roughness increased with the increasing of the deposition temperature. At the short wavelength period the increasing total optical loss at certain deposition temperature was mainly caused by absorption while scattering loss occupied a very low percentage of the whole loss. The absorbance of the samples related to the LIDT was discussed. The increasing absorbance at high deposition temperature attributed to the decreasing of LIDT. And high micro-defect density of sample surface resulted in low LIDT.