Tuning the exponential sensitivity of a bound-state-in-continuum optical sensor

Area of Science:

• Photonics and Nanotechnology
• Optical Sensing
• Metasurface Technology

Background:

• All-dielectric metasurfaces offer unique optical properties.
• Bound states in the continuum (BICs) enable strong light-matter interaction.
• Evanescent field sensing is crucial for detecting subtle changes in materials.

Purpose of the Study:

• To investigate the evanescent field sensing mechanism of a BIC-supporting all-dielectric metasurface.
• To demonstrate its application in refractive index sensing and molecular adsorption detection.
• To achieve high sensitivity and figure of merit (FOM) for sensing applications.

Main Methods:

• Fabrication of a transparent, subwavelength-thick photonic crystal metasurface.
• Utilizing topology-induced confinement for BIC field localization.
• Experimental infiltration of liquids with varying refractive indices (1.33-1.45).
• Numerical analysis to support experimental observations.
• Theoretical engineering for molecular adsorption sensing.

Main Results:

• Experimental observation of exponential sensitivity up to 226 nm/RIU for refractive index sensing.
• Demonstration of excellent figure of merit (FOM).
• Theoretical prediction of potential sensitivities up to 4000 nm/RIU for molecular adsorption.
• BIC field localized normal to the metasurface and delocalized in-plane.

Conclusions:

• The all-dielectric metasurface effectively utilizes BICs for high-performance evanescent field sensing.
• The demonstrated sensing mechanism shows promise for versatile and multiplexing sensing schemes.
• The technology holds significant potential for label-free molecular detection and other sensing applications.