A flexible metamaterial with negative refractive index at visible wavelength

•We demonstrate a flexible metamaterial with negative index at visible range.•A design rule to make negative refraction by changing lattice constants is proposed.•A fabrication process for flexible and free-standing metamaterial is suggested.

In this paper, we demonstrated a realization of a flexible metamaterial with negative refractive index operating at visible wavelength. With the help of Finite-Difference Time-Domain (FDTD) method, we could establish design rules for the metamaterial and analyze the characteristics of it. To this end, the fishnet structure with the unit cell size 185 nm by 240 nm was fabricated. Due to the polymer dielectric spacer between the metal-layers, the metamaterial is freestanding without base substrate and additional backside etching process.