Control Of Metamaterials On Electromagnetic Waves And Application Of Memamaterials On Solar Radio Observations

A new type of artificial microstructure that can realize special electromagnetic regulation has been a hot topic of modern science and technology.The metamaterial is a type of novel artificial electromagnetic microstructures.Because it may have arbitrary permittivity and permeability different from those of natural materials,the metamaterial has many special electromagnetic characteristics,such as negative refractive index,inverse doppler effect,super-resolution Imaging and so on.In particular,one type of metamaterials with hyperbolic dispersion is called the hyperbolic metamaterial(HMM)which support the high-k waves.Based on the abnormal dispersion characteristics of high-k waves,it has the better ability to manipulate the propagation of electromagnetic waves.In recent years,there are many theoretical and experimental researches on HMM,but photonic microstructure composed of hyperbolic metamaterials and conventional materials still need more attention and profound studies.Because metamaterilas have special electromagnetic characteristics,they are used to develop new kind of antennas with good performance.Though there are many applications on metamaterial antennas,it isn't reported in the field of solar radio observations.Since the microwave is the window to develop radio astronomy observations,it has the great significance to study the solar radio astronomy equipments as part of radio astronomy equipments.The overall performance of radio astronomy equipments is affected greatly by the antenna.At present,in GHz frequency ranges,conventional radio telescopes mainly use the parabolic antennas which are usually large,heavy and difficult to maintain.Therefore,we study subwavelength memamaterial planar antennas based on the locally resonant coupling mechanism of the electromagnetic field.This new kind of planar antennas has small volume and is easy to be conformal with other components,but it has high gain and directivity.This will pave the way to the next-generation radio astronomy equipments consisting of matematerial antennas with a smaller and planar configuration,which is also important for putting such radio astronomy observational systems in space(as satellites,space stations,etc.)in future..The main contents of this dissertation include two sections.The first section mainly introduces the manipulation of abnormal band-gap and photonic localization based on artificial microstructures containing HMM.The other section introduces the theoretical and experimental studies on new kind of metamaterial antennas and solar radio telescopes for solar radio observation.In chapter 2,we studied the artificial photonic microstructures which is composed of hyperbolic metamaterials and dielectic materials in the ultraviolet and visible regions.Theoretical and experimental studies were carried out simultaneously.This chapter is divided into two parts.(1)In this part,we present the experimental demonstration of angle-independent gaps in the visible wavelength range in onedimensional photonic crystals composed of layered hyperbolic metamaterials and dielectrics.HMM with anomalous wave-vector dispersion can tune the propagating phase of light to an unprecedented extent that usual dielectrics cannot attain.The hyperbolic metamaterials is mimicked by the layered titanium dioxide and silver with a subwavelength unit cell.Based on the phase-variation compensation effect between the HMM and the dielectric,an angle-independent gap is experimentally realized,which agrees well with the simulated one.This angle-independent gap is very useful in the design of photonic devices such as omnidirectional reflectors with fixed bandwidth or all-angle filters.(2)We theoretically and experimentally investigate the wide-angle perfect absorptance in a photonic heterostructure composed of a metal film and a truncated photonic crystal with layered hyperbolic metamaterials in the near ultraviolet and visible regions.The wide-angle perfect optical absorption depends on the dispersionless Tamm plasmon polariton(TPP)under TM polarization,which originates from reflection phase compensation condition between the metal and the truncated photonic crystals with HMM.Our experimental results show nearly perfect absorptance over 0.91 in an angle range of 0-45 degree,which facilitates the design of perfect optical absorbers working in a wide angle range.In chapter 3,We made systemical theoretical and experimental studies about metamaterial antenna with excellent radiation characteristics and a kind of new solar radio telescopes based on metamaterial antenna.This chapter is divided into four parts.(1)We present a kind of large area subwavelength cavity antenna with artificial permeability-negative metamaterials at GHz range.The antenna has the advantages of flatness,ultra-thin thickness,high gain and good directivity.The optimal receiving area of the antenna is mainly determined by the size of the radiation source.Its directivity and sidelobe cancellation mainly depend on the patterns of the patch array as the radiation source.It is found that the antenna with non-uniform distributed patch array as the radiation source has better performance than that with uniform distributed patch array patterns.Otherwise,this type of metamaterial antenna has nearly the same performance compared to that of parabolic antenna with equal radiation aperture,so it has potential applications to replace the traditional large aperture parabolic antenna.Moreover,in order to realize the monitoring of solar radiation flows at multiple frequencies,several sets of metamaterial antennas are designed where the test performance and simulation performance of the antenna are in good agreement.(2)We study a kind of metamaterial planar antenna with one subwavelength cavity to realize multi-frequency resonances.The metamaterial antenna can independently radiate or receive electromagnetic signals at two different frequencies by using double-layer metamaterials,which has the characteristics of ultra-thin thickness,high gain and good direction at two different resonant frequencies.The test performance and simulation performance of the metamaterial antenna are in good agreement.(3)In order to observe the circular polarization electromagnetic signals of solar radio radiations,we study a kind of circularly polarized metamaterial antenna with circular-polarization selective subwavelength resonant units.This new kind of antennas has a simple configuration and can realize high circular polarized performance without complex feed systems.The test performance and simulation performance of the antenna are in good agreement.(4)Based on subwavelength cavity metamaterial antenna,we have developed a new kind of F107 solar radio flux telescope.This solar radio telescope is used to observe F107 solar radio flux for a long time.The observation data is in good agreement with that obtained from abroad equipments.