Research On The Design And Performance Of The Devices Based On Zero-refractive Index Metamaterials

In the electromagnetic metamaterials,zero-index metamaterials including ε-near-zero material(ENZ)whose permittivity is close to zero,μ-near-zero material(MNZ)with near-zero permeability,με-near-zero material(MENZ)that both the permittivity and permeability approach to zero and anisotropic near-zero index metamaterial have drawn considerable attention in both fundamental and applied research due to their novel proprieties such as tunneling effect,directional radiation and phase tailoring effect.This thesis focuses on the factors influencing the transmission properties,the effective ways to modulate the properties of zero-refractive index metamaterials and the approach to realize some photonic devices based on zero-refractive index metamaterials.1.Influence of the propagation properties of zero-refractive index metamaterialsIn order to exploit the potential applications of zero-refractive index metamaterials,we study the properties of some composite structures based on zero-index metamaterials.Firstly,we investigate the influence of an air slit on the transmission of an ENZ with defects.The air slit almost has no influence on the transmission of electromagnetic wave in the structure before the slit cuts off the structure.When the ENZ with defect is cut off by the slit,transmission characteristics change suddenly.The transmittance decreases sharply and becomes sensitive to the position and the thickness of the air slit.Based on this property displacement sensors with high sensitivity can be realized.Then,we study the transmission properties of a three-dimensional MENZ waveguide with holes at the wall of the waveguide.As long as these holes do not destroy the connectivity of perfect electric/magnetic conductor from the incident port to the output port,the electromagnetic wave goes around these holes and gets through the MENZ waveguide completely.The surface percolation is achieved.It is shown that the three-dimensional MENZ waveguide still has good transmission performance in an open environment.In further,we investigate the propagation properties of the two-dimensional waveguide structure formed by MENZ and ENZ.We find that before the connectivity of MENZ is destroyed,the electromagnetic wave spontaneously goes around ENZ and passes through the waveguide completely via the MENZ.The percolation of the electromagnetic wave occurs in a two-dimensional structure.The transmission properties of the MENZ waveguide with impurities can be enhanced by utilizing the percolation of electromagnetic wave.We also study the transmission properties of acoustic waves in an acoustic double-zero metamateial waveguide with some holes filled with reciprocal of modulus-near-zero metamaterial,and observe similar percolation phenomenon.Our work breaks through the limitation that the percolation phenomenon based on zero-refractive index metamaterials only appears in the system where vector wave transmits and three-dimensional structure.2.Control of the transmission properties of zero-refractive index metamaterials and the design of corresponding devicesFirstly,a magnetically controlled MENZ waveguide and a magnetically controlled MNZ waveguide have been constructed respectively.The transmittance of the two waveguides can be adjusted by the bias magnetic field sensitively in a large range,so that the functions of switches,modulators and magnetic sensors with high sensitivity can be realized.The magnetically controlled MNZ waveguide has higher sensitivity and wider bandwidth,and can be used for an adjustable bandpass filter.Then,a star structure has been constructed by two magnetized ENZs and a metal.We study the propagation mode of the one-way surface wave in response to the applied magnetic field.We propose the design of a modulator with two mirror-symmetric star structures realizing the modulation of magnetic signals effectively.Taking advantage of the unidirectional transmission and the prohibition of bulk modes of magnetized ENZ,the influence of the reflected wave and the side scattering wave on the surrounding devices can be avoided effectively.3.Device design based on multi-lead zero-refractive index metamaterialsWe propose a valve structure consisting of zero-refractive index materials to manipulate the transmission of the electromagnetic wave.Based on the multiple reflections of the electromagnetic wave at the control port,the transmission of the electromagnetic wave is effectively and conveniently controlled without changing the intrinsic properties of zero-index materials.An adjustable anisotropic ENZ bending waveguide,an arbitrary-sized isotropic ENZ waveguide and a polarization-independent MENZ waveguide have been realized.Then the function of the interferometer in the phase demodulator has been realized through zero-index materials with three ports.We discuss the performance of the interferometer when zero-index metamaterial is MENZ and ENZ.By reducing the area of ENZ,introducing a defect and using anisotropic ENZ,the poor performance of the interferometer caused by the mismatched impedance of ENZ can be compensated.Finally,we also investigate the propagation properties of acoustic waves in three-dimensional zero-index metamaterial with several leads.It is found that the propagation of acoustic waves is independent of the shape of the lead’s cross section and the direction of each lead in three-dimensional space.According to this,the beam splitter in three-dimensional space,the coupler of the waveguides with different sections and the interferometer in the acoustic demodulator have been designed.