Research On Design And Performance Of One-dimensional Quasiperiodic Photonic Crystal

Photonic crystal is a type of artificial dielectric material with periodic distribution.It has the characteristics of photon localization,photonic bandgap and suppression of spontaneous emission of photons.As a branch of the photonic crystal family,quasiperiodic photonic crystals have become a research hotspot due to their rich spectral features.Based on the properties and advantages of quasiperiodic photonic crystals,this thesis proposes a design and performance study based on one-dimensional quasiperiodic photonic crystals.The main research contents of the paper are as follows:(1)Two novel types of quasiperiodic photonic crystal structures are introduced,namely quasiperiodic photonic crystals whose refractive index distribution is modulated by a sign function,and quasiperiodic photonic crystals which are logically combined by two periodic photonic crystals.For the former quasiperiodic photonic crystal modulated by a sign function,the bandgaps can be arbitrarily designed,and each bandgap is independent of each other in the spectrum.For the latter photonic crystals composed of logical combinations,studying the Fourier spectrum and reflection spectrum of the refractive index distribution function,we can find a broadband optical response.(2)Based on the pre-designed characteristics of the quasiperiodic photonic crystal modulated by a symbol function,we propose a multimode optical Tamm state(OTS)with a presettable intrinsic wavelength.By analyzing the refractive index distribution and Fourier spectrum of the photonic crystal,it can be found that the forbidden band corresponds to the peak position in the Fourier spectrum.By covering the surface of the photonic crystal with a layer of metal,OTS can be excited in each band gap.Moreover,by adding microcavities to metal and photonic quasicrystal structures,multimode OTS can be observed in a single band gap.Compared with the traditional metal-photonic crystal structure,after introducing quasiperiodic and optical cavities,multiple modes of OTS are exicted.And these OTS have the characteristics of being pre-designed,flexible and adjustable,which introduces more degrees of freedom and methods for the research of optical Tamm-based devices.(3)The parity-time-symmetric(PT-symmetric)structure in the non-Hermit system is a hot research topic in physics in recent years.Studies have shown that in a parity-time-symmetric structure,unidirectional reflectionlessness phenomenon can be obsearved at the Exceptional Point(EP)of the spectrum.Based on this,by introducing PT-symmetry into the quasiperiodic photonic crystal formed by a logical combination,the phenomenon of broadband near-zero reflection caused by the interaction of multiple EP points was found in this structure.At the EP points,the field profile is distributed as an even function in the structure,and a phase transition point emerges.The above structure provides new ideas for further to study of broadband absorption and broadband invisibility.