Method to fabricate orthogonal crossed gratings based on a dual Lloyd's mirror interferometer

• A dual Lloyd's mirror interferometer for making crossed gratings with a single exposure is proposed.
• The angle between the two periodic directions of the crossed grating is solely determined by the normal directions of the two Lloyd's mirrors and the substrate.
• Both theoretical analysis and experimental results demonstrate that the orthogonal crossed gratings' orthogonality error mainly depends on the angle between the two Lloyd's mirrors.

We propose a dual Lloyd's mirror interferometer with two mutually perpendicular mirrors to fabricate orthogonal crossed gratings through a single exposure. Theoretical analysis shows that in this interferometer the angle between two main periodic directions of the crossed grating is solely determined by the normal directions of the two Lloyd's mirrors and the substrate. To verify this theoretical prediction, four groups of crossed gratings were fabricated. The measurement results agree well with the theoretical relationship.