Shen Chen, Tan Xin, Jiao Qingbin, Zhang Wei, Wu Na, Bayan Heshig, Qi Xiangdong
Opt Express. 2018 Sep 17;26(19):25381-25398. doi: 10.1364/OE.26.025381.
A swing ion-beam etching method to fabricate convex blazed gratings used in shortwave infrared hyperspectral imaging spectrometers is presented. This method solves the consistency problem of blaze angles by swing etching through the meridian direction of the gratings. The mathematical relationship of the curvature, aperture, and diffraction efficiency of convex gratings is studied to demonstrate the limitation of conventional translational lithography and the necessity of swing etching. A geometric model is built to analyze the influence of swinging speed and beam slit width on groove evolution. Convex gratings with a 45.5 gr/mm groove density, 67 mm aperture, 156.88 mm radius of curvature, and 2.2° blaze angle have been fabricated and measured where the peak and average diffraction efficiency in the shortwave infrared band reach 90% and 70%, respectively. Experimental results validate that high-efficiency convex gratings of small blaze angle and high groove consistency can be produced by swing etching, which satisfy the requirements for high spectral resolution and miniaturization of imaging spectrometers.
提出了一种用于制造短波红外高光谱成像光谱仪中凸面闪耀光栅的摆动离子束蚀刻方法。该方法通过沿光栅子午线方向摆动蚀刻解决了闪耀角的一致性问题。研究了凸面光栅的曲率、孔径和衍射效率之间的数学关系，以证明传统平移光刻的局限性以及摆动蚀刻的必要性。建立了几何模型来分析摆动速度和束缝宽度对槽演变的影响。已制作并测量了槽密度为45.5线/毫米、孔径为67毫米、曲率半径为156.88毫米、闪耀角为2.2°的凸面光栅，其在短波红外波段的峰值和平均衍射效率分别达到90%和70%。实验结果验证了通过摆动蚀刻可以制造出小闪耀角和高槽一致性的高效凸面光栅，满足成像光谱仪高光谱分辨率和小型化的要求。
