The fraction of the incident radiation which is diffracted into a
single specified order (positive and negative orders treated separately)
as calculated by the scalar diffraction theory as, for example, is described
by H.W. Schnopper et al, Applied Optics 16, 1088 (1977).

Material

The chemical formula is required here. Note that this is case sensitive
(e.g. CO for Carbon Monoxide vs Co for Cobalt).

Density

If a negative value is entered, the chemical formula
is checked against a list of some
common materials.
If no match is found
then the density of the first element in the formula is used.

Gap/Period

Ratio of the gap between the rectangular
grating bars to the grating period.

Grating Bar Thickness

Thickness of the bars in the direction perpendicular to the
plane of the grating.

Fractional grating area

The fraction of the grating area which is not obscurred by the
support structure (=1 if no support mesh).

Support mesh thickness

The thickness of the support mesh only effects the zero order efficiency.

Output

A GIF plot is generated for viewing the results.
For numerical values, follow the link above the GIF plot to an ASCII text file.
For a nice looking printed copy, you might try using the EPS file.