Tuning Characteristics Of Mid-infrared Patch Antennas Based On VO₂

Tunable optical antenna can regulate the amplitude and phase of mid-infrared waves,and can be applied in the field of mid-infrared modulation and detection.In this paper,VO2 phase change material was used in optical patch antenna structure,and a tunable mid-infrared patch antenna sample is fabricated,which exhibits an absorption tuning range of 10% in frequency and modulation depth of 50% and provides a promising solution to manipulate mid-infrared waves.The norelty of this research is as follows.We designed a VO2-based mid-infrared tunable antenna consisting of Au circular patch antenna arrays,a VO2 phase change thin film,a SiO2 buffer layer and Cu substrate,then fabricated the sample by micro-nano fabrication techniques.As measured by FTIR,the antenna sample is observed to have three main antenna resonance peaks at 23.6THz,33.5THz and 47.3THz in the condition of incident angle of 15 degree and TM polarization.As compared with the simulation,the 23.6THz and 47.3THz peaks are attributed to the TM11 and TM12 modes,while the peak at 33.5THz is regarded as coupling mode of two adjacent Au patches.In the process of temperature changing,resonances of this sample can continuously tune from 295 K to 365 K in the mid-infrared range with a red-shift for increasing temperature and a blue-shift for decreasing temperature.The TM12 absorption peak has a maximum tuning range of 4THz and a maximum absorption of 81.6%.Measurements in both heating and cooling processes have revealed that a hysteresis loop of resonance frequency around 340 K which confirms the VO2 phase change phenomenon as an origin of the antennas tuning behavior.At the same time,the antenna is characterized by SEM,XRD and XPS.The characterizations reveal the presence of impurities and different shapes of patch antennas,which can explain the deviations between experiment and simulation.Our demonstrated tunable mid-infrared antenna expands the device application of VO2 phase material in mid-infrared,and provides an innovation solution for manipulate mid-infrared radiations.