Selective terahertz absorber for angle and polarization-independent spectral sensing

Area of Science:

• Optics and Photonics
• Materials Science
• Electrical Engineering

Background:

• Terahertz (THz) technology requires efficient absorbers for applications like imaging and spectroscopy.
• Existing THz absorbers often suffer from polarization or incident angle dependency, limiting their practical use.

Purpose of the Study:

• To design and fabricate polarization- and incident-angle-independent narrow-band terahertz absorbers.
• To enable advanced THz imaging, radar, and spectroscopy applications.

Main Methods:

• Utilized a transparent fused silica (SiOx) substrate with a metal backing and a periodic array of metal cross patterns.
• Employed finite element analysis (FEA) simulations for geometry optimization.
• Fabricated devices using contact photolithography.
• Characterized absorption bands using Fourier-transform reflectance spectroscopy.

Main Results:

• Achieved tunable absorption bands in the 50-200 cm^-1 (1.5-6 THz) range.
• Observed full widths at half maximum (FWHM) of 20-56 cm^-1 (0.6-1.68 THz).
• Measured maximum absorption levels from -8.5 to -16.8 dB.
• Demonstrated absorption bands independent of incidence angle and polarization, consistent with simulations.

Conclusions:

• The developed terahertz absorbers exhibit polarization- and incident-angle-independent narrow-band absorption.
• The tunable nature and robustness of the absorbers make them suitable for various THz applications.
• The design offers a promising solution for enhancing THz technologies.