Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear and nonlinear optical properties. In this work, second-harmonic generation in a hyperbolic metamaterial due to a free-electron nonlinear response of a plasmonic component of the metamaterial is studied. It is shown that owing to a rich modal structure of an anisotropic plasmonic metamaterial slab, the overlap of fundamental and second-harmonic modes results in the broadband enhancement of radiated second-harmonic intensity by up to 2 orders of magnitude for TM- and TE-polarized fundamental light, compared to a smooth Au film under TM-polarised illumination. Compared to the radiated second-harmonic intensity from a bulk LiNbO3 nonlinear crystal of the same thickness, the SHG intensity from a metamaterial slab may be up to 2 orders of magnitude higher at the certain metamaterial resonances. The results open up possibilities to design tuneable frequency-doubling integratable metamaterial with the goal to overcome limitations associated with classical phase matching conditions in thick nonlinear crystals.
- hyperbolic metamaterials
- second harmonic generation