Aplanatic waveguide Fresnel lenses
A new modification of waveguide Fresnel lenses is proposed. The phase-shifting zones in these lenses are located on a curvilinear contour. It is shown that the coma aberration can be eliminated by selecting the contour shape as a circle in an isotropic waveguide and as part of an ellipse in an anisotropic waveguide. Results of a numerical simulation are presented. These demonstrate that the optical characteristics of lenses having a curvilinear contour are improved considerably. It is noted that hybrid planar optical systems free of the lowest-order aberrations can be constructed.