Characteristic analysis for different beamsplitters of the plane holographic grating lithography system
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摘要: 分光器件是全息光栅曝光系统中的关键光学元件,它将入射激光光束分成两束,两相干光束叠加后形成干涉条纹。曝光系统的稳定性不但影响干涉条纹对比度,还影响光栅衍射波前像差、杂散光水平以及光栅掩模刻槽质量。为了提高曝光系统的稳定性,分析入射光束角度偏离与两相干光束夹角(2<em>θ</em>)的关系,并结合干涉条纹周期公式,分别导出了以光栅和棱镜作为分光器件时入射激光束角度偏离量与待制作光栅空间相位差的解析表达式,据此分析了光栅和棱镜曝光系统的稳定性。结果表明,采用光栅分光的曝光系统的稳定性比棱镜分光曝光系统稳定性提高5~6个数量级,这对长时间曝光制作全息光栅具有实际意义。Abstract: The beamsplitter has a critical role in the interference lithography, which splits one laser beam into two, therefore these two waves can interfere to produce the fringes. The instability of the interference lithography, which is determined by the selection of the beamsplitter, not only decreases the contrast of the patterns, but also causes the phase distortion, high scatter light and low quality of the groove. To improve the stability of the interference lithography system, based on the period equation of the fringes and the correction between deviation of the incidence and the interference beam angular variations(2<em>θ</em>), we discuss the phase distortion due to the alignment error of cube and the grating beamsplitter, and analyze the stability of the two different interference lithography system. Results indicate that in the grating manufacture, using the grating as the beamsplitter instead of the cube beamsplitter can increase the stability of lithography system by 5 to 6 orders of magnitude, which has a significant effect on grating fabrication with long-time exposure.
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图 2 不同分光器件分光光束角度变化比较
Figure 2. Angular variation comparison for different beamsplitters
图 3 光束偏离与相干光夹角变化关系
Figure 3. Correlation between the interference angular variation and the angle alignment error
图 4 不同分光器件引起两相干光夹角变化示意图
Figure 4. Angular variations for using the different beamsplitters
图 5 不同分光器件干涉条纹空间相位差与干涉条纹周期的变化曲线
Figure 5. Phase distortion comparison due to the pattern period for different beamsplitters
图 6 不同分光器件条件下光束偏离比较(n=0.25)
Figure 6. Allowable angular instability comparison for different beamsplitters when n=0.25
表 1 不同分光器件导致光栅空间相位差变化(以1 800 gr/mm为例)
Table 1. Phase distortion comparison between the cube and the grating beamsplitters for the same angle alignment error(1 800 gr/mm)
Grating area/mm Cube beamsplitter(n) Grating beamsplitter(n) 30° 45° 60° 
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