Broadband achromatic optical metasurface devices

Abstract

Among various flat optical devices, metasurfaces have presented their great ability in efficient manipulation of light fields and have been proposed for variety of devices with specific functionalities. However, due to the high phase dispersion of their building blocks, metasurfaces significantly suffer from large chromatic aberration. Here we propose a design principle to realize achromatic metasurface devices which successfully eliminate the chromatic aberration over a continuous wavelength region from 1200 to 1680 nm for circularly-polarized incidences in a reflection scheme. For this proof-of-concept, we demonstrate broadband achromatic metalenses (with the efficiency on the order of ∼12%) which are capable of focusing light with arbitrary wavelength at the same focal plane. A broadband achromatic gradient metasurface is also implemented, which is able to deflect wide-band light by the same angle. Through this approach, various flat achromatic devices that were previously impossible can be realized, which will allow innovation in full-color detection and imaging.

Design of task-specific optical systems using broadband diffractive neural networks

“…In addition to such diffractive surfaces, metasurfaces also present engineered optical responses, devised through densely packed subwavelength resonator arrays which control their dispersion behavior [44][45][46][47][48] . Recent advances in metasurfaces enabled several broadband, achromatic lens designs for e.g., imaging applications [49][50][51] . On the other hand, the design space of broadband optical components that process a continuum of wavelengths relying on these elegant techniques have been restrained to single-layer architectures, mostly with an intuitive analytical formulation of the desired surface function 52 .…”

Achromatic reflected metalens for highly directional and long-distance acoustic probing

“…Theoretical and experimental results demonstrates that the position of focal point has a very weak frequency dependence over a broadband. Different from the application of achromatic metalens for full-color camera in optics [2][3][4][5], here a highly directional and long-distance acoustic probing scheme is proposed by a combination of achromatic reflected metalens and triple sensors separated by a subwavelength interval, in which a signal processing method is presented to eliminate the interferences between incident waves and reflected waves, resulting in a highly directional beampattern confirmed by an experiment. Although no interference exists between incident waves and transmitted waves for an achromatic transmitted lens, an achromatic reflected lens has advantages in focusing efficiency and bandwidth, which is a good choice for a longdistance acoustic probing.…”

“…Owing to the development of metamaterials and metasurfaces, optical focusing and imaging by lenses have attracted much attention from scientists, such as a perfect lens for subwavelength imaging [1] and achromatic metalenses for full-color detection and imaging [2][3][4][5]. Advances in optical focusing and imaging have inspired researchers in acoustics to design novel acoustic focusing and imaging devices.…”

Observation of an exceptional point in a non-Hermitian metasurface

“…The significance of exceptional points has frequently been noted in non-Hermitian systems with the special constraint of being parity-time symmetric. In these paritytime symmetric systems the exceptional point was shown to be the point of the parity-time symmetry breaking transition [5][6][7][8][9][10][11]. Beyond being the phase transition point of parity-time symmetric systems, exceptional points have unique properties due to the underlying geometry of their complex parameter spaces.…”