THz time-domain spectroscopy modulated with semiconductor plasmonic perfect absorbers

Area of Science:

• Materials Science
• Photonics
• Semiconductor Physics

Background:

• Terahertz time-domain spectroscopy (THz-TDS) is crucial for THz photonics in civil and defense applications.
• Plasmonic microstructures and metasurfaces enhance THz spectroscopy and sensor development.
• Highly doped semiconductors offer an alternative to noble metals for THz plasmonics.

Purpose of the Study:

• To present a novel perfect absorber structure utilizing semiconductor III-Sb epitaxial layers.
• To demonstrate the potential of engineered semiconductor surfaces for THz applications.
• To explore enhanced light-matter interactions in the THz region.

Main Methods:

• Fabrication of a perfect absorber using GaSb insulator and Si-doped InAsSb (5x10^19 cm^-3) metal-like layers.
• Optical doping measurement in the Infrared (IR) using polaritonic effects.
• Electron beam lithography and dry etching for defining the structure.
• THz-TDS measurements to characterize absorption bandwidth.

Main Results:

• Theoretical engineering of frequency-selective absorption across a broad THz range (1.0–6.0 THz).
• Experimental measurement of a 1350 GHz cumulative bandwidth absorption using THz-TDS (1.0–2.5 THz).
• Absorption bandwidth limited only by the air-exposed reflectance configuration.

Conclusions:

• Semiconductor-based selective surfaces can significantly enhance light-matter interaction in the THz region.
• The developed perfect absorber structure shows promise for advanced THz spectroscopy and sensing.
• This work paves the way for tunable semiconductor metasurfaces in THz photonics.