Subwavelength structures and their use in diffractive optics

A novel design for imitating continuous phase profiles by bi- nary subwavelength structures is presented. The working principle has recently been shown for regular gratings like beam deflectors (Haidner et al., 1993) or polarizing beamsplitters (Collischon et al., 1994). Our objective is to transfer this principle to non-strictly periodic gratings such as lenses and further to avoid the strong polarization dependence by using 2-D modulated subwavelength structures. A further objective is to examine the origin of this effect. Two possibilities exist—the resonance effect, because the structure size is nearly as large as the wavelength, and the averaging effect, which should be responsible if the light can not resolve the small structures. © 1996 Society of Photo-Optical Instru- mentation Engineers. Subject terms: diffractive optics; subwavelength structures; infrared physics; lens design.