Polarization-Insensitive Focusing Lens Using 2D Blocky High-Contrast Gratings

We propose a high-transmissivity, polarization-insensitive focusing lens (PIFL) using 2D blocky sub-wavelength high-contrast gratings (2D-BSW-HCGs). Simultaneously, a design method for 2D-BSW-HCGs PIFL is put forward. A PIFL with high transmissivity can be constructed by designing the transmissivity and phase shift profile of nonperiodic 2D-BSW-HCGs. Properties of focusing and transmission are numerically studied with the finite-element method. The numerical simulation results show that, when the incident wavelength is 1550 nm, the transmissivity is 0.8659, and the numerical aperture (NA) is 0.535. At the focal plane, the field distribution of the average full width at half maximum is 1.7515 μm. Moreover, the design approach also can be expended to a high-NA PIFL and a polarization-insensitive focusing reflector.