Search

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. [ABSTRACT FROM AUTHOR]

We study, by numerical simulations and experimentally, the resonant diffraction by metal (Ag) gratings in the mid-IR ( \sim 10~\mu \textm ) spectral range. The excitation of surface plasmon-polaritons facilitates narrow-band resonantly enhanced diffraction into symmetry-prohibited diffraction orders. We show that, even though the propagation losses for plasmonic modes are greatly reduced at longer wavelengths, the magnitude of the resonant diffraction peak remains limited due to diffraction into other, normally allowed, diffraction orders. The grating depth dependence of the resonant diffraction spectra indicates that with shallower gratings, the Q -factor of the resonance may become as large as 10^{3} – 10^{4}$ , while the magnitude of the peak is reduced. [ABSTRACT FROM AUTHOR]