Remarkable polarization sensitivity of gold nanoparticle arrays

In an array of low-symmetry, L-shaped gold nanoparticles, slight distortions of particle shape and arm lengths eliminate the array’s mirror plane. Such asymmetries induce large angular shifts (∼10°) of the resonant extinction axes directions from those of mirror-symmetric particles. The axes directions exhibit dispersion, as allowed by the lack of any structural features dictating them. The nanostructures are chiral, and evidence of optical activity is observed. Rigorous diffraction theory calculations qualitatively reproduce the data.