A novel silicon-on-insulator microring biosensor based on Young＇s twoslit interference has been demonstrated. The transducer signal from electric field intensity distribution on the interference screen is given by using the transfer matrix method（TMM） and two-slit interference principle.The result shows that the structure we propose is advantageous for sensing as the interference pattern is very sensitive to the ambient refractive index around the microring.A small perturbation in refractive index around the microring△n_c will result in a notable shift of destructive interference points（DIPs） on the interference screen.By detecting the shift of the DIPs,the ambient refractive index change can be obtained.
The effect of shape, height, and interparticle spacing of Au nanoparticles （NPs） on the sensing performance of Au NP array is systematically investigated. Lengthening the major axis of elliptical NPs with the minor axis kept constant will cause the redshift of the local surface plasmon （LSP） resonance mode, enhance the sensitivity, and widen the resonance peaks. Larger height corresponds to smaller LSP resonance wavelength and narrower resonance peak. With each NP size unchanged, larger interparticle spacing corresponds to larger resonance wavelength and smaller full-width at half-maximum （FWHM）. Moreover, duty cycle is important for sensitivity, which is largest when the duty cycle is 0.4.
