Bismuth plasmonics for extraordinary light absorption in deep sub-wavelength geometries

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Metamaterial absorbers are crucial for optical devices.
• Existing absorbers often lack sufficient bandwidth, limiting their applications.
• Metal-insulator-metal (MIM) cavities are a common structure for absorbers.

Purpose of the Study:

• To demonstrate an ultra-broadband metamaterial absorber with unrivaled bandwidth.
• To identify optimal materials for maximizing metal-insulator-metal (MIM) cavity bandwidth.
• To investigate the use of bismuth (Bi) for near-infrared (NIR) metamaterial applications.

Main Methods:

• Theoretical analysis to determine ideal metal properties for MIM cavities.
• Material selection based on n-k data and theoretical predictions.
• Design, fabrication, and characterization of a bismuth nanodisc-based MIM resonator.

Main Results:

• Bismuth (Bi) exhibits ideal optical properties for ultra-broadband absorption in the NIR.
• A Bi nanodisc-based MIM resonator achieved absorption above 0.9 from 800 nm to 2390 nm.
• This represents the broadest absorption bandwidth reported for a MIM cavity in the NIR, exceeding others by over 150%.

Conclusions:

• Bismuth is a superior material for achieving ultra-broadband absorption in MIM cavities.
• Proper material selection and precise dimensions are key to realizing efficient, sub-wavelength optical devices.
• This work paves the way for advanced optical devices with significantly enhanced performance.