Multiple Fano Resonances And Refractive Index Sensing In MIM Waveguide Coupled Resonators

In the rapidly evolving information era,optical devices based on photons have shown considerable potential compared to conventional electronic devices.As the main method of optical field control,surface plasmon polaritons excited by MIM waveguide not only break through the traditional optical diffraction limit,but also have the advantages of easy integration and manufacturing.Meanwhile,Fano resonance is highly sensitive to the change of refractive index in the surrounding environment and its resonance spectral lines are sharp.Therefore,using MIM waveguides coupled resonators to excite Fano resonance to design highly sensitive refractive index sensors is one of the significant ways to convert its advantages into applications.In this thesis,two different types of refractive index sensors have been designed by combining theory and simulation based on the MIM waveguide as sensing structures and multiple Fano resonances effect as sensing fundamentals.To some extent,it overcomes the shortcomings of current Fano resonance in sensing applications and provides ideas for the design of a new type of high sensitivity,high FOM refractive index sensor.The primary research work is as follows:1.Triple Fano resonances refractive index sensing based on MIM waveguide coupled T-type and ring resonators is designed.A sensing structure with the symmetric T-type resonator is proposed,and its transmission spectrum of the structure is analyzed by the finite difference time domain method.The continuous state spectral lines provided by the MIM waveguide with a baffle and the discrete state spectral lines provided by the symmetric T-type resonators interfere to form dual Fano resonances.On this basis,the symmetry of the resonator is further broken,and one of the T-type resonators is replaced by a ring resonator.A Fano resonance mode regulated by the ring resonator appears in the transmission spectrum.Through parameter optimization,the structure can attain the sensitivity of 1012 nm/RIU and FOM of 5.57×10~4in the refractive index range of 1.00-1.10.2.To extend the sensing range,a sensing structure comprised of hexagonal nut and square ring resonator as well as a MIM waveguide with a baffle is designed.The transmission spectrum and optical field distribution of the structure are obtained by the finite difference time domain method.The structure can gain five Fano resonances and be tuned by different resonators.Under the optimal parameters,the sensitivity of 998nm/RIU and the FOM of 49016 under the gas sensing range of 1.00-1.10,and the sensitivity of 1030 nm/RIU and the FOM of 14890 under the liquid refractive range of1.30-1.40 have been attained.Its excellent sensing performance has great application prospects in refractive index sensing fields such as biomedicine and chemistry.