Several Infrared Optical Properties And Applications Of Metamaterials

The infrared occupies 0.3-400 THz in the electromagnetic spectrum(wavelength0.75-300?m in vacuum).Research on infrared waves are of potential use in the areas of the thermal emitter,infrared detection,thermal imaging,radiative cooling,and infrared camouflaging.The mid-infrared spectral range(3-25?m)contains highly characteristic molecular bonds,is often called"molecular fingerprint"regions.The mid-infrared(8-15?m)has a reputation as"life light"medically,it's helpful for promoting biological growth,enhances human immunity and metabolism.The two main atmospheric transparency windows,3.5?5.5?m and 8?12?m,are also in the infrared band.Therefore,it has important significance in the study of working mechanisms and functional devices of infrared metamaterials.Metamaterials regulate the macroscopic physical properties through the micro-nano structure design,so it has abundant degrees of freedom in the control of optical parameters.And it is considered as a good platform for infrared electromagnetic wave research.Numerous studies have shown that surface plasmon polaritons,surface phonon polaritons,magnetic polaritons,optic Tamm states,and their coupled states can be used to realize the modulation of material optical parameters and infrared electromagnetic fields.Besides,numerous new mechanisms,new properties,and new functions are still needed to be further explored and discovered.The main research directions of this thesis are the infrared optical properties and applications of metamaterials.This thesis focuses on the following three aspects:the regulation of infrared thermal radiation,absorption,and metamaterial resonance coupling.The main contents are as follows:In chapter I,we were given an overview of the origin,the development of metamaterials.Then,we focus on the metamaterials regulation of radiation properties,such as thermal radiation spectrum,the electromagnetic resonance model,and the coupling of electromagnetic resonance.In chapter II,we focus on introducing the electromagnetic resonance model of metamaterials and the general analysis theories.There is surface phonon polariton,optical Tamm states,magnetic polariton,and their energy band theory.In addition,three general theoretical models of metamaterials are introduced:transfer matrix method,LC circuit model,and temporal coupled-mode theory.In chapter III,we investigated spectrally selective thermal emitters'properties and applications of optic Tamm states.First,a wafer-scale,lithography-free,refractory,and narrowband aperiodic multilayered metamaterials(AMM)thermal emitter device in the MIR regions is proposed and experimentally demonstrated,through the genetic algorithm(GA)based inverse design.The basic structure is composed of alternating refractory dielectric materials niobium pentoxide(Nb₂O₅)and silica(Si O₂)deposited on refractory metallic material chromium(Cr).Finally,as a proof-of-concept demonstration of potential applications,MIR emission images and infrared formaldehyde(CH?O)gas sensing tests under high-temperature conditions were conducted to verify the versatile functionality of our proposed devices.Relative sensitivity increase by a factor of 10 can be obtained concerning the value of the broadband blackbody reference system.We believe that the proposed approaches can be implemented for the refractory light sources,allowing applications in thermal imaging and optical gas sensing.In chapter IV,we investigated the magnetic polarization resonance mode of phonon polariton and the strong coupling of the SPh P in the grating of 6H-Si C.We propose a robust equivalent circuit model for the accurate prediction of magnetic polariton(MP)resonances in Si C grooves.By considering the boundary effects and introducing a parasitic capacitance.With the model,we further propose the MP absorber with a broad bandwidth successfully.We believe this robust circuit model offers us opportunities in the design of novel applications based on MPs such as filters,detectors,and coherent sources in the infrared fields.On the other hand,we investigated the polarization sensitivity of the Si C grating structure and analyzed the resonance of polarization in detail.We report the strong coupling occurs in the microstructures consisting of an one-dimensional 6H-Si C grating.Furthermore,such strong coupling is sensitive to the polarization of the incident light and the orientation of the gratings.The dipole antenna resonances and the edge-coupling surface phonon polaritons with near-zero group velocity are revealed to be responsible for the strong coupling theoretically and experimentally.We believe that our study offers new possibilities towards mid-infrared detection devices.In chapter V,we are focusing on the active control of electromagnetically induced transparent(EIT).First,we theoretically investigate the dynamical control of EIT metamaterials loaded by low-lossy graphene in near-infrared frequencies,e.g.,light slowing within the induced transparent window.Coupling with graphene enables distinctive optical responses of the“bright”and“dark”resonators in EIT metamaterials,rendering a switching of the transparent window and modulation on light dispersion.We show that the active modulation on optical properties of the transparent window enabled by low-lossy graphene is distinctive either by passively adjusting the interspacing between the building blocks of EIT metamaterials or active tuning by high-lossy graphene.Furthermore,we report that the group refractive index can be in situ tuned dynamically over a broad range,e.g.,?2 orders for near-infrared frequencies,together with absorption maintained at a level similar to that of the unloaded structure.Our study offers new possibilities towards chip-scale devices,such as active optical switching,filtering,and data storing.In chapter VI,we discuss the outlook of my thesis and outline its future direction.