The Research Of Active Mid-infrared Optical Devices Based On The Phase-change Material

Electromagnetic metasurfaces have many unnatural and peculiar electromagnetic physical characteristics,and have attracted great attentions in recent years.Phase change materials have been induced in the field of metasurfaces due to the ability of tunable electromagnetic response,which has given a new impetus to the development of this field.Based on the phase change material Ge₂Sb₂Te₅?GST?,two tunable optical devices are proposed in the mid-infrared band:perfect absorber and filter,and their properties are analyzed theoretically.The research contents of this dissertation are listed as follows:?1?A polarization-independent and tunable perfect absorber based on GST metasurfaces in the mid-infrared band is proposed.Based on the conventional metal-insulator-metal three-layer structure,we introduce phase change material GST with a high refractive index in the dielectric layer.Under illuminating normal incident light,the upper metal structure parameters are optimized to match the impedance of the incident surface,and a gap plasmon resonance is induced inside the structure,so that the structure produces an efficient light reflection in the mid-infrared band resulting in a reflection dip that is the light absorption peak.Withchanging GST phase,the absorption peak can still achieve absorption efficiency of more than 86%in the wavelength range of 5.3⁶.3?m.The high-efficiency absorption spectrum can be used to detect the change of refractive index of the external environment.The theory of splitting energy can also be used to study the absorption spectrum of a molecule.?2?A polarization-independent and tunable metamaterial filter based on GST metasurfaces in the mid-infrared band is proposed.It adopts a cylindrical array structure using high refractive index GST which can excite the Mie resonance under illuminating normal incident light.Multipole scattering cross section and electromagnetic near-field distribution show that the resonance type of the amorphous GST cylinder at 3.55?m is magnetic dipole resonance,and the initial resonance position of the magnetic dipole is optimized by changing the size parameter.The phase of the GST can also control the resonant wavelength of the magnetic dipole,which will obtain a broad spectrum filtering.Finally,the effects of the polarization state and incident angle of the incident light on the transmission peak are studied separately.The results show that based on this structure,an efficient filter can be obtained in the mid-infrared to avoid the interference in the working band.