Polarization-insensitive achromatic metalens based on computational wavefront coding

Abstract

Broadband achromatic metalens imaging is of great interest in various applications, such as integrated imaging and augmented/virtual reality display. Current methods of achromatic metalenses mainly rely on the compensation of a linear phase dispersion implemented with complex nanostructures. Here, we propose and experimentally demonstrate a polarization-insensitive achromatic metalens (PIA-ML) based on computational wavefront coding. In this method, simple circular or square nanopillars are individually coded such that the focal depths at wavelengths at both ends of the achromatic bandwidth overlap at the designed focal plane, which removes the limitation of requiring a linear phase dispersion. An optimized PIA-ML that works in the full optical communication band from 1300 to 1700nm was obtained using a particle swarm optimization algorithm. Experimental results show that both focusing and imaging of the fabricated metalens are consistent with theoretical predictions within the broadband wavelength range, which provides a new methodology for ultra-broadband achromatic imaging with simple-shaped nanostructures.

Large-scale achromatic flat lens by light frequency-domain coherence optimization

“…However, metalenses still severely suffer from poor imaging quality under broadband illumination due to serious chromatic aberration [10][11][12][13] . Several pioneering works have demonstrated achromatic metalens operating over a broad wavelength range [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] . However, according to the fundamental limitations of the achromatic flat lens, the diameter of an ideal achromatic metalens (under the diffraction limit) is restricted by its thickness (the max height each nano-unit can achieve) [18][19][20][32][33][34] .…”

High-Efficiency Plasmonic Metalens for Dual-Polarization Imaging with a Single Set of 3D Variable Nanostructures

“…In addition, the function of those elements is usually limited to the polarization filtering. Recently, optical metasurfaces with various manipulation characteristics of the light wave have been proposed and demonstrated, such as achromatic imaging metalens, − optical hologram, , and polarization control and conversion. − Moreover, the multifocal polarization-dependent metalenses have also attracted lots of attention due to the superior characteristics of multiple functions, lightweight, and integration, from which the incident light with different linear or circular polarization states is focused/imaged at different positions. − In 2016, Khorasaninejad et al demonstrated a multispectral chiral imaging metalens in the visible wavelength band, in which two sets of TiO 2 nanopillar arrays corresponding to right-handed circular polarization (RCP) and left-handed circular polarization (LCP) states, respectively, were arranged as the Pancharatnam–Berry phase (P–B phase) . The lights with different CP states and wavelengths are, therefore, imaged at the different positions by the two sets of metalens.…”

Large-scale achromatic flat lens by light coherence optimization

“…Several pioneering works have demonstrated achromatic metalens operating over a broad wavelength range [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] . However, according to the fundamental limitations of the achromatic flat lens, the diameter of an ideal achromatic metalens (under the diffraction limit) is restricted by its thickness (the max height each nano-unit can achieve) [18][19][20][31][32][33] .…”