Synthesis of zero index of refraction metamaterials via frequency-selective surfaces using genetic algorithms

The paper presents a novel technique for the synthesis of thin, planar, low-loss, easily-realizable materials which exhibit a low or near zero index of refraction. These zero index metamaterials (ZIM) are realized via frequency-selective surfaces (FSS), the parameters of which are determined by a genetic algorithm in response to specific design goals, such as frequency of operation, refractive index, and amount of loss. Potential uses for these new zero index materials include superstrates or substrates for focusing the radiation patterns of microstrip antennas, signal phase manipulation and equalization, and other imaging applications. A design example is presented which achieves ℜ{n}=-0.36 and a transmission loss of only 3.5 dB at 10 GHz, while remaining simple to fabricate and interface to a printed-circuit microstrip patch antenna. This technique is an offshoot of current research into the use of genetically-optimized planar FSS to realize materials with a negative index of refraction.