High-figure-of-merit refractive index sensing assisted by quasi-bound state in the continuum

What is it about?

Refractive index sensing has received enormous attention due to its potential applications in monitoring concentration of biological analytes or gas, temperature, and humidity. Assisted by surface plasmon polaritons or localized surface plasmon resonances, researchers greatly improved the sensitivity of the refractive index sensing. However, the figure-of-merit is limited due to the inevitable optical absorption of metals. In this work, we have realized quasi-bound state in the continuum in an all-dielectric compound grating waveguide structure. Assisted by the quasi-bound state in the continuum, the figure-of-merit of refractive index sensing is greatly improved.

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Photo by Clyde He on Unsplash

Photo by Clyde He on Unsplash

Why is it important?

Over the past several decades, surface plasmon polaritons or localized surface plasmon resonances have been widely utilized to achieve sensitive refractive index sensing. However, the figure-of-merit is limited to hundreds of RIU^(-1) due to the inevitable optical absorption of metals. In our work, we have utilized a quasi-bound state in the continuum in an all-dielectric compound grating waveguide structure to achieve sensitive refractive index sensing. Owing the ultrahigh quality factor of the quasi-bound state in the continuum, the figure-of-merit can be greatly improved to thousands of RIU^(-1).

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