SUBWAVELENGTH STRUCTURES AND THEIR USE IN DIFFRACTIVE OPTICS

A novel design for imitating continuous phase profiles by binary subwa velength structures is presented. The working principle has recently b een shown for regular gratings like beam deflectors (Haidner et al., 1 993) or polarizing beamsplitters (Collischon et al., 1994). Our object ive is to transfer this principle to non-strictly periodic gratings su ch as lenses and further to avoid the strong polarization dependence b y using 2-D modulated subwavelength structures. A further objective is to examine the origin of this effect. Two possibilities exist-the res onance effect, because the structure size is nearly as large as the wa velength, and the averaging effect, which should be responsible if the light can not resolve the small structures. (C) 1996 Society of Photo -Optical Instrumentation Engineers.