| Photonic crystals(PCs)are a kind of micro-nano structures formed by periodic arrangement of materials with different refractive indices.One of the basic characteristics of PCs is photonic bandgap(PBG),which means that electromagnetic waves in a certain frequency range can’t propagate in the periodic structures.This property can be adjusted to form PBG in different frequency ranges.Another basic feature of PCs is photonic localization,which means that defect states will appear in PBG when defects are introduced into PCs,and the photonic energy of the defect state will be confined within the defect region,while electromagnetic waves away from defect frequency will decay rapidly in the PBG.Based on these properties,PCs have been widely used in many fields,such as photonic chip,spectroscopy and etc.Ion irradiation technology is a method that using ion acceleration device accelerates ions so that ions have higher kinetic energy and they are injected into materials so as to change the local composition and structure of materials.The advantage of ion irradiation is that it can precisely control the energy,dose,depth distribution and uniformity of injected elements,and there is no limit to the types of injected elements.In the field of optics and photonics,ion irradiation technology has been widely used to change the optical properties of optical materials,and many optical devices have been developed.In this paper,ion irradiation technique is combined with PCs.PCs are irradiated by highenergy ions to adjust photonic bandgap and defect mode.In this paper,the optical properties of monolayer films and various PCs under different ion irradiation conditions are studied theoretically and experimentally.In the second chapter,SiO2 and TiO2 monolayers as well as a variety of PCs structures composed of SiO2 and TiO2 were prepared,and above structures were irradiated with O ion with 3MeV energy and different radiation doses to study the changes of their optical properties.After O ion irradiation,the refractive index of the monolayer increases and the thickness of the monolayer decreases,which leads to the decrease of the optical thickness.Moreover,the change of optical parameters caused by O ion on the monolayer material is basically consistent with the effect of O ion on the PCs.Ion irradiation results in blue shift of PBG and defect mode.In addition,the irradiation increases the optical absorption of materials,and results in lower transmittance and reflectance of PCs.In the third chapter,a variety of PCs structures composed of SiO2 and TiO2 were prepared,and above structures were irradiated with C ion with 3MeV energy and different doses to study the changes of their optical properties.C ion irradiation results in the decrease of optical thickness of the basic unit of PCs,which results in the blue shift of the PBG and defect mode.The blue shift of the PBG and defect mode increases with the increase of ion irradiation dose.In addition,the transmittance and reflectance of PCs decrease simultaneously,indicating that C ion irradiation leads to enhanced optical absorption of materials.The change of optical properties of PCs caused by ion irradiation can be used to develop tunable photonic crystal filters,optical switches and optical absorbers and etc. |
