The paper presents the investigation on anti-reflection property of subwavelength cross-gratings with relief profile close to pyramid or cone. Such gratings are polarization independent and have effective refractive index increasing gradually from the top to the substrate. Theoretical analysis indicates that, to obtain good anti-reflection effect, for normally incident lights in visible band (400 ∼ 700 nm) the grating period should not be larger than 266 nm. Cross gratings with different periods were fabricated using holographic double-exposure method on photoresist. Measurements show that the grating with 255 nm period has higher transmittance compared with the gratings with the periods larger than 266 nm. Measurements also show that larger grating depth results in higher transmittance. The experimental results are in good agreement with the theoretical analysis.

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