天文望远镜用全息阶梯光栅

As a significant dispersive element, echelles with a lower density and a large blazed angle were usually used for astronomical spectrometers. Echelles are needed for a large aperture Optical/infrared telescope in order for high resolution and throughout, and thus it is also a key technique for the construction of a large aperture astronomical telescope of our country in the future. However, it is difficult, time-consuming and high cost for ruling technique, which usually was used to fabricate echelles in the past tens of years, to fabricate large-area echelle gratings with a density of hundreds of grooves per millimeters, low stray light and a high wave-front quality. .As far as holographic lithography, the grooves over the entire area are formed simultaneously at a time by using double beam interference such that the groove profile can be expected to be more uniform, thus it is faster than ruling and a high wave-front quality can be obtained. Moreover, holographic gratings offer significant advantages in spectrometric systems where stray light and ghost intensity are performance limiting. Firstly, with scanning holographic lithography techniques, smooth grating patterns are record in photoresist covering on the surface of a fused silica as the mask of the following process, then a holographic echelle with triangular grooves is obtained by using ion beam etching. In this project，it will be explored how to generate the triangle-groove profile, especially that with 90 degree apex angle in ion beam etching.

阶梯光栅作为天文光谱仪的核心色散元件，线条密度低，闪耀角度大。大尺寸阶梯光栅应用于大口径光学/红外望远镜以获得高的频谱分辨率与高光通量，是我国未来大口径天文望远镜急需的关键技术。对于目前常用的阶梯光栅制作技术——机械刻划，研制沟槽密度几百线/毫米，且具有低杂散光与高质量衍射波前的大尺寸阶梯光栅，成本高、时间长、难度大。 .全息光刻使用双光束干涉，一次性在大尺寸基底上获得均匀的光栅图形，研制周期短，能保证高质量衍射波前，尤其具有无鬼线，低杂散光之优点。本项目拟首先使用扫描全息光刻技术，在石英基底表面产生平直光滑的光刻胶光栅掩模，再利用离子束刻蚀融石英获得三角形槽的全息阶梯光栅，研究离子束刻蚀过程中，光栅槽型的演变过程，以及顶角为直角的三角形槽的控制方法。

本项目旨在通过全息离子束刻蚀技术，开展大闪耀角阶梯光栅结构技术研究，解决将来大口径天文望远镜所需全息-离子束刻蚀大尺寸阶梯光栅研制的关键问题。项目使用全息光刻产生了333线/mm光栅图形，该线密度参考了我国空间站无缝光谱仪拟需要的透射闪耀光栅参数，使用离子束刻蚀技术，在50×110mm石英玻璃基底表面进行大闪耀角的透射光栅结构的研制技术，并研制出首块光栅样品。检测结果显示，光栅透射衍射波前PV0.2波长，在300-1000nm波段，衍射效率峰值达到72%，杂散光水平显著降低。实现对光栅槽型演变过程的量化控制，参数可重复。现有实验结果已达到预期目标，后期将继续该课题研究，推进相关技术在我国天文观测光栅的工程应用。