Research On Negative Refraction And Focusing Properties Of One-Dimensional Photonic Crystal

Photonic crystal(PC),one of most typical artificial microstructure materials,naturally possesses attractive characteristics of photonic bandgap and capacity of phonon localization,which endows it promising prospective in designing various micro/nano-optical devices such as,omnidirectional reflector,all-optical diode,optical filter,microcavity laser and so on.Theoretical and experimental researches have revealed that,PC can be excellent negative refraction material under certain manipulations of structure and permittivity,and can perfectly exhibit negative refraction characteristics.This,consequently,has drawn enormous interest in studies of achieving subwavelength focusing and super-resolution imaging,and presents great potentials in optical manipulation,nanolithography,data storage and optical microscope.In this dissertation,the negative refraction and focusing properties of 1D-PC are theoretically and numerically investigated.The main research contents include following aspects:1.Based on 1D-PCs,a wedge-shaped prism model was designed to verify its negative refraction effect.According to equal frequency surface method,effective refractive index of 1D-PC at certain wavelength was accurately calculated and corresponding effective refraction angle was achieved with Snell’s law.In addition,the relationship between effective refractive index/effective refraction angle and wavelength locating at second band was investigated.Using the finite element method,the relationship between effective refraction angle of 1D-PC wedge-shaped prism and wavelength in second band was analyzed,whose calculated results are compared with that calculated by equal frequency surface method.2.Based on 1D Thue-Morse PQCs,a wedge-shaped prism model was designed to verify its negative refraction effect.Under Bragg conditions,the relationship between transmission spectra of 1D Thue-Morse PQC and number of Thue-Morse sequences was studied.Moreover,with certain sequence number,the relationship between transmission spectrum and center wavelength was studied.At certain center wavelength,the relationship between transmission spectrum and refractive index of medium was studied.The negative refraction band of the 1D Thue-Morse PQC are obtained by analyzing the transmission spectrum,dispersion relation of 1D periodic photonic crystal(PPC)and the transmission spectrum of 1D Thue-Morse PQC.The refraction angle of 1D Thue-Morse PQC wedge-shaped prism is obtained by using the finite element method.The relationship between refraction angle/effective refractive index and wavelength locating at negative refraction band was studied.3.Based on 1D-PCs,a cylindrical symmetry plano-concave lens model with focusable cylindrical vector beam(including radially polarized beam and azimuthally polarized beam)was designed.At certain wavelength in second band,the focusing properties of the cylindrical symmetry plano-concave lens for radially and azimuthally polarized beams are analyzed.4.Based on 1D Thue-Morse PQCs,a ID Thue-Morse PQC cylindrical symmetry plano-concave lens model is designed to focus with cylindrical vector beam.Under Bragg conditions,the relationship between band structure and focusing wavelength of this lens is confirmed.Furthermore,the focusing effects of lens was analyzed in different focusing band,and the calculated results was compared with that of 1D-PC cylindrical symmetry plano-concave lens under same parameters.