TECHNIQUES FOR MANUFACTURING VARIABLE ETCH DEPTH GRATINGS USING GRAY-TONE LITHOGRAPHY

A method of fabricating gratings with variable grating depths including depositing a first grating material layer with a uniform thickness profile on a substrate, forming an etch mask layer having a variable thickness profile on the first grating material layer, etching the etch mask layer and the first grating material layer to change the uniform thickness profile of the first grating material layer to a non-uniform thickness profile, forming a patterned hard mask on the first grating material layer, and etching, using the patterned hard mask, the first grating material layer to form a grating with a variable depth in the first grating material layer.