Figure A1.

(a) Optical image (reflection) of Au microparticles on Si substrate. (b) Reflection spectral mapping of Au microparticles (pairs) patterned at ${\Lambda }_{x,y}=10\mathsf{\mu }$m array at two perpendicular polarisations; map taken at 2800 cm${}^{-1}$ or 3.57 $\mathsf{\mu }$m or 83.94 THz. Circular markers are locations of Au microparticles of ∼0.7 $\mathsf{\mu }$m. Au microparticles were LIFT transferred from 50 nm film by using $NA=0.26$ objective lens at pulse energy $E_p=816$ nJ. Separation between Au microparticles 3 $\mathsf{\mu }$m. The light source is Australian Synchrotron. The mapping was carried out by MCT detector with a scanning pinhole aperture of 3 $\mathsf{\mu }$m. The reference was flat Si substrate.