A multiresolution direct binary search iterative procedure is used to design small dielectric irregular diffractive optical elements that have subwavelength features and achieve near-field focusing below the diffraction limit. Designs with a single focus or with two foci, depending on wavelength or polarization, illustrate the possible functionalities available from the large number of degrees of freedom. These examples suggest that the concept of such elements may find applications in near-field lithography, wavelength-division multiplexing, spectral analysis, and polarization beam splitters.
© 2006 Optical Society of America
Diffraction and Gratings
Original Manuscript: December 2, 2005
Revised Manuscript: February 1, 2006
Manuscript Accepted: February 2, 2006
Jia-Han Li, Kevin J. Webb, Gerald J. Burke, Daniel A. White, and Charles A. Thompson, "Design of near-field irregular diffractive optical elements by use of a multiresolution direct binary search method," Opt. Lett. 31, 1181-1183 (2006)