Dear Hua-Tang Chen
What do you mean when you say grating mask? Is it phase mask, a grating on
a glass substrate, that can restore a grating pattern when exposed with
UV-light?
If it is the case please check the following web site: http://www.ibsen.dk/
. If you have more specific questions about phase masks feel free to mail
to info@ibsen.dk
regards, Mounir Ennabli