Exploring plasmonic gradient metasurfaces for enhanced optical sensing in the visible spectrum.

Area of Science:

• Nanophotonics and Metasurface Technology
• Optical Sensing and Biosensing

Background:

• Conventional optical sensors have limitations in sensitivity, complexity, and size.
• Existing metasurface sensors are restricted by narrow detection bandwidths due to reliance on high-Q resonances and wavelength shifts.

Purpose of the Study:

• To introduce a plasmonic gradient metasurface-based sensor (PGMS) for wide-spectrum refractive index detection.
• To overcome the bandwidth limitations of previous metasurface sensor designs.

Main Methods:

• Utilized the Pancharatnam-Berry phase method for a 2π phase shift, enabling simultaneous specular and deflected beams.
• Employed a far-field intensity ratio (I* = I_+1/I_0) to amplify optical response by maximizing deflected beam intensity and minimizing specular reflection.
• Incorporated a normalization factor to enhance sensing performance and versatility for broadband applications.

Main Results:

• Demonstrated consistent performance across diverse media and wavelengths, overcoming oxidation issues.
• Achieved broadband refractive index sensing with enhanced sensitivity, particularly in green wavelengths.
• The PGMS shows potential for visible spectrum applications, including biomedical diagnostics and environmental monitoring.

Conclusions:

• The developed PGMS offers a significant advancement over conventional optical sensors and previous metasurface designs.
• This technology enhances sensitivity and adaptability for broadband optical sensing.
• The PGMS is suitable for visible spectrum applications like biomedical diagnostics and environmental monitoring.