Metamaterials 8 Refractive index 8 Analytical expressions 6 Energy gap 6 Frequency ranges 6 Negative index 6 Positive index materials 6 Forbidden band 4 Interference mechanisms 4 Multilayers 4 Quasi-periodic 4 Aperiodic photonic structures 2 Aperiodic structure 2 Band gaps 2 Band-gap edge 2 Constitutive parameters 2 Dispersion (waves) 2 Dispersion models 2 Electronic equipment 2 Fibonacci 2 Geometry 2 Light radiation 2 Light refraction 2 Light wave 2 Lower limits 2 Metamaterial 2 Negative refractive index 2 Non-periodic multilayers 2 Periodic multilayers 2 Positive-index materials 2