The invariance of the direction of a given order diffracted by a grating used in conical diffraction (i.e., in off-plane mounting) when the grating is rotated about a suitable direction is established. The extension of this property to crossed gratings (2-D gratings) is demonstrated. An explanation of this amazing property is given in terms of Fermat's principle and applies to any reflecting surface.
© 1985 Optical Society of America
Original Manuscript: October 6, 1984
Published: January 15, 1985
D. Maystre, M. Neviere, and W. R. Hunter, "Geometrical invariance property of gratings," Appl. Opt. 24, 215-216 (1985)