  Hyperbolic plasmonic metamaterials provide numerous opportunities for
designing unusual linear and nonlinear optical properties. We show that the
modal overlap of fundamental and second-harmonic light in an anisotropic
plasmonic metamaterial slab results in the broadband enhancement of radiated
second-harmonic intensity by up to 2 orders of magnitudes for TM- and
TE-polarized fundamental light, compared to a smooth Au film under TM-polarised
illumination. The results open up possibilities to design tuneable
frequency-doubling metamaterial with the goal to overcome limitations
associated with classical phase matching conditions in thick nonlinear
crystals.
