Diffraction characteristics of <i>N</i>-level (5 ≤ <i>N</i> ≤ 8) binary gratings fabricated by repetition of three sets of photolithography and dry-etching processes have been investigated. After presentation of the general algorithm to determine a mask pattern and etching depth combination used in each fabrication process, all the methods for creating staircase structures with <i>N</i> = 5, 6, 7, 8 are derived. Then the diffraction efficiency achievable for the different level numbers, with the existence of mask alignment errors and for a fixed grating period, is compared, and it is found that an eight-level structure does not always give the best value.
© 1998 Optical Society of America
(050.1380) Diffraction and gratings : Binary optics
(050.1970) Diffraction and gratings : Diffractive optics
(220.0220) Optical design and fabrication : Optical design and fabrication
(230.1950) Optical devices : Diffraction gratings
Yasuyuki Unno, "Fabrication of N-Level Binary Optical Elements by Use of M Mask Patterns with N in the Range of 2M-1 + 1 ≤ N ≤ 2M," Appl. Opt. 37, 8012-8020 (1998)