  Plasmonic resonances in metallic nanostructures have been shown to
drastically enhance local electromagnetic fields, and thereby increase the
efficiency of nonlinear optical phenomena, such as second harmonic generation
(SHG). While it has been experimentally observed that enhanced fields can
significantly boost SHG, to date it proved difficult to probe electrical and
magnetic resonances in one and the same nanostructure. This however is
necessary to directly compare relative contributions of electrical and magnetic
components of SHG enhancement. In this paper we report an experimental study of
a metasurface capable of providing electrical and magnetic resonant SHG
enhancement for TM polarization. Our metasurface could be engineered such that
the peak frequencies of electrical and magnetic resonances could be adjusted
independently. We used this feature to distinguish their relative
contributions. Experimentally it was observed that the magnetic resonance
provides only 50% as much enhancement to SHG as compared to the electric
resonance. In addition aligning both resonances in frequency results in
conversion efficiency of 1.32 x 10^(-10).
