Wide-angle and full-angle negative reflection based on metasurfaces with specific surface phase gradient

摘要

Metasurface, an ultrathin planar profile novel wavefront manipulating device, is a hot spot of research on metamaterials in recent years. As for metasurface having a constant surface phase gradient, it can be totally described by the generalized law of refraction and reflection, which has been theoretically and experimentally verified perfectly. According to the generalized Snell's law, there exists a limited range of incident angle which enables the existence of negative reflection and refraction, and anomalous reflection and refraction is also limited to take place at the domain defined by the critical angle. However, wide-angle or even full-angle negative reflection and refraction is desired for their huge potential of novel wavefront modulation applications. In the present work, we discuss the possibility of wide-angle and full-angle negative reflection through the generalized law of reflection, and point out that wide-angle negative reflection can be obtained when the surface phase gradient of metasurface is greater than the operating wavenumber and full-angle negative reflection can be obtained when the surface phase gradient of metasurface is equal to the operating wavenumber. In order to test the validity of our theory, we calculate the reflected acoustic field of two acoustic metasurfaces which having surface phase gradient greater than and equal to the operating wavenumber accordingly. The metasurfaces we use here are composed by deep subwavelength comb-like subunits which are able to manipulate the reflected phase from 0 to 360 degree with near unit reflection coefficient and thus provide more advantages in realizing the large surface phase gradient on demand with acceptable wavefront modulation precision. Simulation results verify the wide-angle and full-angle negative reflection perfectly and any novel acoustic wavefront modulating devices that take advantage of negative reflectionMetasurface, an ultrathin planar profile novel wavefront manipulating device, is a hot spot of research on metamaterials in recent years. As for metasurface having a constant surface phase gradient, it can be totally described by the generalized law of refraction and reflection, which has been theoretically and experimentally verified perfectly. According to the generalized Snell's law, there exists a limited range of incident angle which enables the existence of negative reflection and refraction, and anomalous reflection and refraction is also limited to take place at the domain defined by the critical angle. However, wide-angle or even full-angle negative reflection and refraction is desired for their huge potential of novel wavefront modulation applications. In the present work, we discuss the possibility of wide-angle and full-angle negative reflection through the generalized law of reflection, and point out that wide-angle negative reflection can be obtained when the surface phase gradient of metasurface is greater than the operating wavenumber and full-angle negative reflection can be obtained when the surface phase gradient of metasurface is equal to the operating wavenumber. In order to test the validity of our theory, we calculate the reflected acoustic field of two acoustic metasurfaces which having surface phase gradient greater than and equal to the operating wavenumber accordingly. The metasurfaces we use here are composed by deep subwavelength comb-like subunits which are able to manipulate the reflected phase from 0 to 360 degree with near unit reflection coefficient and thus provide more advantages in realizing the large surface phase gradient on demand with acceptable wavefront modulation precision. Simulation results verify the wide-angle and full-angle negative reflection perfectly and any novel acoustic wavefront modulating devices that take advantage of negative reflection can be designed and fabricated in future. can be designed and fabricated in future.