Realization of a Two-Dimensional Isotropic Metamaterial: Fabrication of Metallic Structures Based on Stimulated Emission Depletion (STED) Direct Laser Writing (DLW)

Abstract

Negative index metamaterials have given rise to a wide range of possible new applications, such as ultrahigh-resolution imaging or cloaking. Simultaneous negative effective permeability and negative electric permittivity have been realized, using two-dimensional fabrication techniques. However, these designs are one-dimensional (1D), as they are operational only in a one-dimensional k-space.

Recently two-dimensional isotropic negative index metamaterials have been designed at communication wavelength [1]. Due to the inherently connected nature with the next-unit-cell neighbors of this design, Direct Laser Writing (DLW) offers great solution to the challenge of manufacturability of these complex structures. Direct Laser Writing has proven to be a versatile lithography tool over the past decade. The possibility of creating nearly arbitrary three-dimensional structures has found many applications in photonics and biology. Its major drawback, however, is the resolution, which is limited to λ/10 by diffraction laws. The resolution of stimulated emission depletion (STED) microscopy [2] is conceptually diffraction-unlimited and features down to λ/90 can be resolved [3]. The purpose of STED-inspired Direct Laser Writing (STED-DLW) is to translate this improvement to three-dimensional lithography [4].