Achromatic Metalens Design And Simulation Based On Guided Mode Resonance

Metalens,as one of the related applications of metasurfaces,has received a lot of attention in recent years.The metalens is a two-dimensional planar structure composed of basic nano units.By changing its geometric parameters and arrangement,it can achieve the expected phase modulation of the incident light in the sub wavelength range,so that it has the function that traditional optical lens does not have.In order to study the application of the metalens in color mixing and color holography,several kinds of the metalens including the achromatic metalens are designed based on guided mode resonance principle,geometric phase principle and achromatic principle.The following contents are studied in this paper:A filter structure with adjustable output wavelength and high transmittance is proposed to realize the output of any wavelength in the visible light band.According to the principle of guided mode resonance,the filter structure is designed with aluminum material as grating,titanium dioxide material as waveguide layer,alumina material as protective layer of aluminum grating and silica material as base layer.By adjusting the grating period,the structure can achieve high transmittance output of any wavelength light in the visible range.A high numerical aperture metalens with three primary colors is designed to realize diffraction limited focusing at the focal point.In the visible light band,titanium dioxide material is selected as the basic unit of the metalens,which is arranged on the substrate composed of silicon dioxide material in turn,and the size of the unit structure is optimized.According to the principle of Pancharatnam-Berry phase modulation,the phase modulation depth from 0 to 2π and the numerical aperture of 0.85 are achieved by adjusting the azimuth of the nanofin.An achromatic metalens with high numerical aperture is proposed to realize diffraction limited focusing of incident visible light.An achromatic metalens is designed by combining a high transmittance filter structure based on guided mode resonance with the three-primary color metalenses to realize achromatic focusing of three primary color light.The achromatic metalens are designed in different regions to filter and focus the trichromatic light.The simulation results show that the achromatic metalens can achieve diffraction limited focusing with a numerical aperture of 0.85 and a focusing efficiency of 34%.