Broadband on-chip near-infrared spectroscopy based on a plasmonic grating filter array

Area of Science:

• Photonics and Spectroscopy
• Nanotechnology
• Materials Science

Background:

• Conventional near-infrared (NIR) spectroscopy systems are often bulky and expensive.
• Miniaturization of spectroscopic systems is crucial for portable and on-site analysis.
• Plasmonic nanostructures offer unique optical properties for developing compact photonic devices.

Purpose of the Study:

• To demonstrate an ultra-compact, broadband on-chip NIR spectroscopy system.
• To achieve high spectral resolution using a novel plasmonic filter array design.
• To validate the system's performance for NIR sensing applications.

Main Methods:

• Fabrication of a monolithic filter array with 28 subwavelength metallic gratings on a gold film.
• Integration of a polymer waveguide layer to generate narrow-band guided-mode resonances.
• Coupling of guided-mode resonances with surface-plasmon resonances of metallic gratings.

Main Results:

• The on-chip system covers a 270 nm spectrum from 1510 nm to 1780 nm.
• The filter array exhibits narrow transmission bands with a full width at half-maximum of 7 nm-13 nm.
• NIR absorption spectroscopy of xylene showed excellent agreement with conventional Fourier transform infrared spectroscopy.

Conclusions:

• The developed ultra-compact plasmonic filter array enables high-resolution NIR spectroscopy on-chip.
• The system demonstrates significant potential for various NIR sensing applications.
• This technology paves the way for portable and cost-effective spectroscopic analysis.