Two-Dimensional (2D) layered materials have garnered interest due to their novel optical and electronic properties. In
this work, we investigate Second Harmonic Generation (SHG) in Tungsten Disulfide (WS2) monolayers grown on
SiO2/Si substrates and suspended on a transmission electron microscopy grid; we find an unusually large second order
susceptibility, which is nearly three orders of magnitude larger than common nonlinear crystals. We have also developed
a Green’s function based formalism to model the harmonic generation from a 2D layer .
We demonstrate a flexible thin film zero refractive index optical metamaterial with matched impedance to free space and
low absorption loss at 1.55 μm. The metallo-dielectric multilayer structure with fishnet geometry was optimized by a
genetic algorithm. The fabrication process and characterization approach are described. The experiment results agree
well with the theoretical predictions, showing an effective index of neff = 0.072 + 0.51i and an impedance of Zeff/Z0 = 1.009 – 0.021i.