Nano-optical manipulation of large in-plane momentum component of wavefront

Abstract

Optical wavefront control is the key to realize every optical application, for laboratories, industries, national security, and personal devices. Recently, lots of nanostructure-based optical wavefront manipulations have been demonstrated to realize ultra-compact of optical devices, such as metasurface hologram, meta-lens, and meta-spectropolarimeter. Metasurface, the arrangement of sub-wavelength nanostructures, allows manipulation of wavefronts with a sub-wavelength spatial resolution. It can support unlimited control of the propagating direction without multiple diffraction orders by the ultra-thin optical film. Studies of controlling the in-plane momentum (propagation direction) while displaying the holographic image by controlling the wavefront with the sub-wavelength resolution have not yet been reported. The methods for active control of the interaction between light and optical nanostructures to support actively controllable high in-plane momentum of wavefronts are required to overcome the limitations of conventional wavefront modulators such as the birefringence of liquid crystals and the fringing effect of the electric field. In this thesis, we present studies on the manipulation of large in-plane momentum components of wavefront based optical nanostructure in the two themes. The first is metasurface based holographic stereogram, which explains the strategies to achieve free control of in-plane momentum and display angle-dependent three-dimensional holographic images by manipulating the amplitude and phase distribution of the wavefronts. Also, we demonstrate a wide viewing angle from −50$^\circ$ to +50$^\circ$ degrees using 212 $\mu$m × 70 $\mu$m metasurface containing 180179 nanostructures. The second is the nanoantenna array for active phase control pixels, which introduces the method to achieve wavelength-scale active phase control pixels using the combined structure of nanoantenna array and liquid crystal. Here, we figure out appropriated nanostructure to support full phase control with 1 −µm-thick liquid crystal layer and demonstrate active phase control by the fabricated optical nanostructures.