Fabrication of high-efficiency and low-stray-light grating by inductively coupled plasma(ICP) etching-polishing method.

Gratings with stray light of 4.99 × 10^-7-5.67 × 10^-7 and efficiency of 93%-95% in a wavelength range of 1592 nm-1632 nm on Si-surface-modification SiC, fused silica and BK7 have been fabricated by the method of ICP etching-polishing. The CHF₃ and SF₆ plasma were used to etch a preliminary grating profile. Ar and O₂ plasma with low energy were then used to polish the grating to acquire low surface roughness and groove profiles closer to the ideal profiles. The morphologies of the gratings were characterized by AFM. The efficiencies and stray light were measured quantitatively by self-developed equipment. These results show that the ICP etching-polishing method is a promising candidate for production of good quality gratings into common optical materials.