In fabricating a diffractive optical element the ratio of the etching depth
between the (n - 1)th and the nth mask is usually 1/2. We found that the d
iffraction efficiency of a diffractive optical element can be improved by a
s much as 7.8% if the above ratio (1/2) is not kept constant. For achieving
this improvement the difference between the desired and the actual diffrac
tion pattern is also used as an objective function for phase quantization.
(C) 2001 Optical Society of America.