Abstract:
In this paper, a comparative study between elliptical ring and square ring resonator sensor, coupled to a metal-insulator-metal (MIM) waveguide is theoretically studied and numerically simulated by finite difference time domain (FDTD) method with a perfectly matched layer absorbing boundary condition. Sensing area of elliptical ring and square ring resonator is being made equal. Major and minor radius of elliptical ring resonator are
obtained by multiplying a converting factor (k = 0.5643) with outer and inner length of square ring respectively. Some parameters like width of elliptical ring and square ring resonator, refractive index of insulator waveguide and width of insulator waveguide are kept same in both the designs. Silver is taken as metal in MIM structure whose frequency dependent relative permittivity is characterized by Drude model. Variation in resonance wavelength occurs when
there is a change in refractive index of material to be sensed. Both the structures are compared for their sensitivity of detecting change in RIU for per change in wavelength. A large value of sensitivity is achieved with square ring resonator when it is compared with elliptical ring resonator. Thus, the square ring resonator can be used in designing highly sensitive refractometer.
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