1000线/毫米软X射线自支撑闪耀透射光栅的设计与制作

Design and fabrication of 1000 line/mm soft X-ray freestanding blazed transmission gratings

基于标量衍射理论讨论了软X射线自支撑闪耀透射光栅的特性并设计了光栅的结构参数.采用全息光刻和湿法腐蚀技术,成功制作了周期1μm、占空比0.1—0.2、高宽比约100、栅线厚度10μm、有效面积比为65%的自支撑闪耀透射光栅.单元尺寸为15mm×15mm的硅绝缘体上含有四个5 mm×5 mm的自支撑闪耀透射光栅窗口.在国家同步辐射实验室检测了该光栅在5—50 nm波长范围内的衍射效率.波长扫描测量结果表明,闪耀效应明显地发生在类似镜面的光栅侧壁镜面反射方向上,闪耀级次位置及其特征与标量理论预测的一致.衍射效率的实测结果基本与理论模拟符合,只是因光栅结构上的缺陷致使衍射效率偏低,峰值只有理论值的38%—49%.实验结果证明了闪耀透射光栅的概念和湿法制作工艺的可行性.

The performance prediction of freestanding blazed transmission grating is discussed using scalar diffraction theory, and grating design parameters are accodingly given. A freestanding transmission grating with a period of 1 lxm, duty cycle of 0.1-0.2, aspect ratio of about 100, thickness of 10 μm and fractional area of 65% is successfully fabricated by holographic lithography and anisotropic wet etching. The size of a single die is 15 mmx 15 mm divided into four 5 mmx 5 mm windows. The diffraction efficiency of the fabricated grating is tested at the National Synchrotron Radiation Laboratory in a wavelength region of 5-50 nm. The wavelength scanning results show a strong blazing effect in the direction of specular reflection from mirror-like grating sidewalls, as expected. The measured and normalized diffraction efficiency is consistent with the theoretical prediction within 38%-49% due to grating structural imperfections. These experimental results prove not only the concept of blazed transmission grating but also practicability of the fabrication process.