Spatially and spectrally engineered spin-orbit interaction for achromatic virtual shaping

Abstract

The geometries of objects are deterministic in electromagnetic phenomena in all aspects of our world, ranging from imaging with spherical eyes to stealth aircraft with bizarre shapes. Nevertheless, shaping the physical geometry is often undesired owing to other physical constraints such as aero- and hydro-dynamics in the stealth technology. Here we demonstrate that it is possible to change the traditional law of reflection as well as the electromagnetic characters without altering the physical shape, by utilizing the achromatic phase shift stemming from spin-orbit interaction in ultrathin space-variant and spectrally engineered metasurfaces. The proposal is validated by full-wave simulations and experimental characterization in optical wavelengths ranging from 600 nm to 2800 nm and microwave frequencies in 8-16 GHz, with echo reflectance less than 10% in the whole range. The virtual shaping as well as the revised law of reflection may serve as a versatile tool in many realms, including broadband and conformal camouflage and Kinoform holography, to name just a few.

Principles of electromagnetic waves in metasurfaces

“…The abrupt phase change could be utilized to achieve wave-front engineering for both planar optical devices such as flat lenses and orbital angular momentum (OAM) generators [30,60,63,64]. The integrated OAM generation may find applications in high-speed communications.…”

“…Clearly, the cross-polarized part has a phase shift proportional to the orientation angle, which is typically termed as geometric phase or optical spin-orbit interaction [60]. Except from the orientation angle, the phase shift will be influenced by the frequency variation of t u and t v .…”

Ultra-wideband manipulation of electromagnetic waves by bilayer scattering engineered gradient metasurface

“…Based on the great freedom of P-B phase, we can design arbitrary phase proles F along the interface by rotating the optical axis a to achieve the virtual shaping. 25 According to above design procedure, we arrange a linear planar phase distribution F(x, y) ¼ lk 0 r/P on an area of 280 Â 280 mm 2 ,…”

“…[10][11][12][13][14][15][16][17][18] For example, distinct from the electromagnetic absorption in subwavelength structures, 19,20 scattering engineering based on metasurface offer an alternative method for low delectability, [21][22][23][24] which could be considered as a virtual shaping technology. 25 However, most existing metasurfaces suffer from a limited operation bandwidth.…”

A high-performance broadband terahertz absorber based on sawtooth-shape doped-silicon

“…The need for high-performance THz absorber is increasing due to both the academic application and military requirement to provide concealment. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] In the past few years, doped silicon has been introduced to improve the THz absorption efficiency and bandwidth. [22][23][24][25][26][27] As a desirable lossy material at THz frequency, doped silicon can support surface plasmon polaritons and accordingly localized surface plasmon resonances via periodic structures.…”