Application Of Nano Antennas With Epsilon-near-zero Materials

Epsilon-near-zero(ENZ)material has become a research hotspot of nano-optoelectronic devices due to its tunable optical properties,fast optical response and low loss.It has been reported to exhibit unprecedented ultrafast nonlinear efficiency over subwavelength propagation lengths.Its excited ENZ mode can be applied in many fields such as perfect absorbers,sensors,all-optical switches,photoelectric modulators,optical emitters,optical isolators,etc.In this paper,the interaction between ENZ mode and surface plasma(LSPR)mode is used to combine the near-zero dielectric constant material with the nanoantennas,and three kinds of nanoantennas with better performance and different functions are designed,which have flexible and wide practical significance.The details are as follows:Firstly,we design a metal nano-antenna based on indium-doped tin oxide(ITO)to achieve a perfect absorber.Among them,ITO is a doped transparent conductive oxide,which is the most widely used material with near-zero dielectric constant.Perfect absorber is the main application of ENZ materials,but after a lot of research,there are still some problems such as low absorption efficiency or narrow absorption band.In addition,many designs have Angle dependence and polarization sensitivity,so the application scope is not wide.In order to solve the above problems,we creatively introduce the trapezoidal metal nanantenna,balance the input impedance and gain of the nanantenna,through the finite Difference Time domain(FDTD)simulation,select the most appropriate inclination,so as to obtain the maximum field enhancement effect.Through the insertion of 15 nm ITO film,the interaction between ENZ mode and LSPR mode by excitation method will make the absorption curve flatter,and the TiN antireflection layer is added to achieve better absorption effect,so that the high absorption band with a width of290 nm near 1310 nm band,the absorption effect is more than 90%.In this study,the influence of Angle and polarization mode is considered.The nano-antenna involved has wide Angle characteristics and polarization insensitivity,and the working range can be adjusted flexibly by changing the carrier concentration of ITO,which makes the application range more extensive.Secondly,we design a nanoantenna sensor based on ITO,which is based on the interaction between plasma-induced transparency and ENZ mode.Previous studies focused on single-band or dual-band sensors,but the structure we designed can realize three-band sensors.By inserting ITO into the antenna array and dielectric layer with four different Au nanorods as units,transmission peaks of three bands are formed by using different coupling modes of open mode,dark mode and ENZ material.By adjusting the parameters of Au nanorods and the carrier concentration of ITO,the position of each transmission peak can be adjusted directionally,and the simulation is still realized by FDTD method.The calculated maximum sensitivity and optimal value coefficient are 330.57 THz/RIU and 27.54/RIU respectively.Compared with other similar sensors,the performance of the sensor designed by us has been significantly improved.Finally,a hybrid plasma waveguide all-optical switch based on ITO is designed and numerically simulated by FDTD method.The mobility of ITO’s free carrier concentration near the communication wavelength is highly amplified by the nonlinear optical effect caused by ENZ materials,resulting in the structure of metal-insulator-semiconductor-insulator-metal(MISIM)has the characteristics of low propagation loss,and the light is limited in the sub wavelength range.The ON and OFF states of the alloptical switch are changed by applying a voltage to the grid.We theoretically analyze the 12.15 dB extinction ratio,0.5 dB insertion loss and 24.3 optimization coefficient at 1550 nm wavelength,and carry out reliability studies on regulating waveguide width and height,which will affect the performance of on-chip switch design,which is necessary for integrating all-optical switches with future silicon photonic circuits.An exploration scheme is provided for ultrafast switching applications.Although our study is only a theoretical simulation without experimental results to support it,it can still guide the direction of future experimental research.Because of the singular properties of ENZ materials,the future research in related fields will still be a hot spot.