Research On The Characteristics Of Fano Resonator And Perfect Absorber Based On FDTD Algorithm

Photonic devices will become an important support and guarantee for the development of next-generation information technology by virtue of their advantages of fast transmission rate,large bandwidth,low loss,and low interference.Improving the integration of photonic devices and achieving ultra-miniaturization of photonic devices are the key to the development of photonic devices.However,due to the existence of the diffraction limit,the size of the photonic device is difficult to break through the sub-wavelength size.Therefore,surface plasmons that can overcome the diffraction limit have become a key technology for the design and manufacture of integrated photonics devices.Based on the surface plasmon resonance,two Fano resonance systems based on the MIM waveguide structure and a thriple-band perfectly absorbing metamaterial structure are constructed in this paper.The finite difference time domain method is used to construct the model and carry out simulation calculation and optimization.There are mainly the following aspects:(1)Designed and studied two Fano resonators based on different MIM waveguide structures:One is a Fano resonator based on a cross-shaped cavity coupled with a MIM waveguide structure.Simulation software based on finite difference time domain(FDTD)is used to simulate and analyze the optical transmission characteristics and field distribution characteristics of the waveguide structure.Three obvious Fano resonances were obtained,and the transmittances of the three Fano resonance peaks were 0.64,0.45 and 0.68,respectively.By optimizing the structure and the refractive index of the medium,the Fano resonator finally obtained has a Fano resonance peak and trough only 6 nm apart,and its sensitivity is as high as 1290 nm/RIU.The design of this structure provides a theoretical basis for refractive index sensing and the integration of electronic circuits.Three Fano resonance of another plasmonic waveguide system composed of isosceles resonators coupled with nanorod defects.The multimode interference coupled mode theory(MICMT)and the finite difference time domain method(FDTD)are used to explain the triple Fano resonance.The results show that the line shape of Fano resonance can be independently tuned by geometric parameters such as the radius of the nanorod defect,the height of the isosceles triangle resonator,or the length of the bottom.For FR2,the transmittance of the system can drop drastically with the change in the wavelength range of only 8nm.The sensitivity and FOM*(quality factor)of FR2 can reach 1250nm/RIU and 88.68 respectively.It has relatively excellent sensitivity and high quality factor,and can be applied to slow light devices,nano-scale filters,refractive index sensors and other related plasma devices.(2)The metamaterial perfect absorber based on plasmon resonance was studied,and the three-frequency,narrow-band perfect absorber with high absorptivity in the visible-near infrared range was designed,and the three-frequency(?1=733 nm,?2=877 nm,?3=1340 nm)are all above 95%(95.2%,99.5%,99.2%)perfect absorption.The refractive index sensitivity reached 398 nm/RIU,425 nm/RIU and 728 nm/RIU,respectively.The absorption peak can be adjusted by changing geometric parameters such as the thickness of the silver layer and the dielectric layer,and the nanopore size period.In addition,the proposed optical absorber also has good angular tolerance.Based on the above advantages,the structure can have many applications,including plasma absorption switches,plasma modulators and high-sensitivity refractive index sensors.