Diffractive phase elements based on two-dimensional artificial dielectrics

This paper presents a method of using two-dimensional subwavelength gratings for the design of artificial dielectric optical elements. It is predicted that an effective continuous index gradient can be obtained by methodical variations of fill factor across a period of the deflection grating. A diffractive lens would result from creation of an index variation in the radial direction. Pyramidal gratings would provide antireflection properties which could be introduced into the diffractive phase element. An extra duty cycle can be applied for adjustment of the birefringence. Design, fabrication, and testing of a grating in fused quartz for use at 633-nm wavelength is described.