Multipole decomposition, second harmonic far-field distribution and nonlinear dissymmetry factor as a function of number of turns of a nanohelix. The inset shows the helix geometry, with linear and nonlinear results for (a) N = 0.5, (b) N = 1, and (c) N = 1.5. Geometric parameters of each helix are p = 200 nm, d = 100 nm, and r = 50 nm. All polar plots are normalized to the maximum forward scattering for RCP excitation.