Possibility of negative refraction for visible light in disordered all-dielectric resonant high index metasurfaces

Abstract

Effective refractive index of disordered all-dielectric metasurfaces consisting of gallium phosphide (GaP) spheres is studied by means of three-dimensional finite-difference time-domain (FDTD) simulations at the wavelength of 532 nm. It is shown that a mixture of the high index nanoparticles with sizes close to the first magnetic and electric resonances randomly dispersed on metasurface may possess negative refraction. The dependence of the metasurface effective refractive index on the nanoparticle concentration and size is constructed. The feasibility of negative refraction at large concentrations of the high index resonant spheres is demonstrated.

Optical Kerr Nonlinearity of Disordered All-Dielectric Resonant High Index Metasurfaces with Negative Refraction

“…This value is close to one computed in Ref. [6]: n 0 eff = −0.40 ± 0.02. Here, f is expressed as ratio of the net volume of the spheres to the volume of the smallest rectangular parallelepiped containing these particles.…”

“…The behavior of n 0 eff (r 2 ) for r 1 = 101 nm is in close agreement with that obtained in Ref. [6] accounting for the absorption of GaP as long as it is sufficiently low. The effective linear refractive index abruptly drops and becomes negative when both r 1 and r 2 reach the sizes of the magnetic and electric dipole Mie resonances.…”

“…As shown in Ref. [6], the densely packed bidisperse monolayer of GaP spheres with the radii r of 77 and 101 nm exhibits the negative refraction at λ = 532 nm. These sizes lie just above the dipole magnetic (r = 76 nm) and electric (r = 100 nm) Mie resonances whose values are calculated using Debye formulas [14,15],…”

“…The possibility of negative refraction by the disordered metasurface consisting of GaP spheres with two radii close to the first magnetic and electric Mie resonances was demonstrated in Ref. [6]. However, until now, the effective Kerr nonlinearity of the negative index metamaterials has not been evaluated.…”

“…The computations in Ref. [6] were conducted for the finite extinction coefficient of GaP (κ = 0.0026). This study neglecting the extinction coefficient show the similar result for the monolayer of 77 and 101 nm radius particles, the influence of κ on the linear optical properties of the GaP metasurface at λ = 532 nm is below the standard deviation value for the computed value of the index of refraction.…”