Subwavelength Focusing Light by Gradient Microoptics
This chapter demonstrates that graded-index Mikaelian lenses and Maxwell “fisheye” lenses, widely known in optics, may also be considered as candidates for subwavelength focusing. The simulation using the FullWAVE software implementing the finite-difference time-domain (FDTD) approach has shown that by combining the HS lens with a subwavelength grating or using a binary hyperbolic secant lens with subwavelength features the focal spot size can be reduced by 10% and 20%. Simulation using the FullWAVE software has shown that by combining the gradient-index HS lens with a subwavelength diffraction grating or replacing the lens with it binary analog the focal spot size can be reduced by 10% and 20% when compared with the diffraction-limited size in the medium. The simulation was conducted by the FDTD method with a space sampling of λ/100 and simulation time of 200λ/c, with c being the speed of light in vacuum.