Chiral plasmonic nanostructures: Experimental and numerical tools

A combination of electron- and ion-beam lithographies has been applied to fabricate patterns of plasmonic nanoparticles having tailored optical functions: they create hot-spots at predefined locations on the nanoparticle at specific wavelengths and polarizations of the incident light field. Direct inscribing of complex chiral patterns into uniform nano-disks of sub-wavelength dimensions, over extensive 20-by-20 μm2 areas, is achieved with high fidelity and efficiency; typical groove widths are in 10-30 nm range. Such patterns can perform optical manipulation functions like nano-tweezing and chiral sorting. Fabrication procedures can be optimized to pattern thin 0.1-2.5 μm-thick membranes with chiral nanoparticles having sub-15 nm grooves. Peculiarities of optical force and torque calculations using finite-difference time-domain method are presented.