Angle and Polarization Tunability of Third-Order Nonlinear Optical Properties in Hyperbolic Multilayer Metamaterials

One of the greatest requirements of nanophotonics are metamaterials with properly engineered linear and nonlinear optical response by structure design and able to actively manipulate light at the nanoscale. In this work, hyperbolic multilayers with different metal filling fractions are fabricated and their third-order optical nonlinearities are investigated at different angles with TE- and TM-polarized light. A continuous modulation of the nonlinear absorption coefficient and the nonlinear refractive index is revealed as a function of the light incidence angle. A model is proposed to predict the angle- and polarization-dependent nonlinear parameters taking into account the optical anisotropy and the local intensity enhancement within the metamaterials.