Subwavelength Grating Lens with Continuous Phase Shifts

Planar optical device with continuous phase shifting (CPS) has raised widespread interest recently. Formed by subwavelength micro/nano structures, planar optics are able to control wavefront in multi aspects including phase and polarization. Most phase shifters for CPS devices are individual structures such as cylinders or cuboids. In this study, we specifically discuss grating based continuous phase shifting lenses comparing with aforementioned counterparts, in terms of differences of design mechanism and polarization responses. In addition we found that grating based metalens has outstanding potential in generating emerging artificial focus pattern. A grating based CPS lens with 'U' shaped focus was fabricated and characterized for prove of concept. Planar optics with artificial focus pattern has great potential for future applications including micro beam shaping and maskless nano lithography.