High-Efficiency Visible Transmitting Polarizations Devices Based on the GaN Metasurface

Abstract

Metasurfaces are capable of tailoring the amplitude, phase, and polarization of incident light to design various polarization devices. Here, we propose a metasurface based on the novel dielectric material gallium nitride (GaN) to realize high-efficiency modulation for both of the orthogonal linear polarizations simultaneously in the visible range. Both modulated transmitted phases of the orthogonal linear polarizations can almost span the whole 2π range by tailoring geometric sizes of the GaN nanobricks, while maintaining high values of transmission (almost all over 90%). At the wavelength of 530 nm, we designed and realized the beam splitter and the focusing lenses successfully. To further prove that our proposed method is suitable for arbitrary orthogonal linear polarization, we also designed a three-dimensional (3D) metalens that can simultaneously focus the X-, Y-, 45°, and 135° linear polarizations on spatially symmetric positions, which can be applied to the linear polarization measurement. Our work provides a possible method to achieve high-efficiency multifunctional optical devices in visible light by extending the modulating dimensions.

Keywords: high-efficiency; metasurfaces; orthogonal polarization; polarization analyzer.

Figure 1

Schematic of the designed unit cell: p = 260 nm, d = 300 nm, and h = 800 nm.

Figure 2

Transmitted light normalization: (a) Transmittance variation for gallium nitride (GaN) nanobricks on Al₂O₃ substrate, and (b) phase as a function of l and w for normal incidence of the X-polarized light. (c,d) The normalized transmittance and phase as a function of l and w for normal incidence of the Y-polarized light, respectively.

Figure 3

(a) The normalized transmittance and the phase of transmitted light through the eight unit cells for the X- and Y-polarized light incidences at wavelength of 530 nm. The inset in (a) is a supercell composed of eight unit cells. (b,c) The electric field distributions for X- and Y-polarized light, respectively; it can be clearly seen that X- and Y-polarized light is refracted into two different directions.

Figure 4

The transmittance of X- and Y-polarized light as a function of deflection angle (θ) under 45° polarized light incident on the bottom.

Figure 5

The distribution of transmitted intensities (|E|²) under the linear polarization states of incident light are (a) 0°, (b) 30°, (c) 42°, (d) 45°, (e) 60°, and (f) 90°. The white solid and dashed lines are the intensity distribution curve and the position of focal plane.

Figure 6

Schematic of the structure array of the designed 3D metalens.

Figure 7

The distributions of transmitted intensities (|E|²) in the focusing plane (X–Y) under (a) X-, (b) Y-, (c) 45°, (d) 135°, (e) 30°and (f) 60° linear-polarized incidences.

Figure 8

The transmitted intensity (|E|²) profiles in focal plane at (a) y = −1560 nm and (b) x = −2080 nm under the incidence of 45° linear-polarized light.