Dichroism mapping at terahertz frequencies via polarization-sensitive computational imaging

Area of Science:

• Physics
• Materials Science
• Engineering

Background:

• Terahertz (THz) non-destructive evaluation (NDE) faces industrial adoption challenges due to high costs, component fragility, and lengthy acquisition times.
• Accurate characterization of anisotropic materials like wood requires spatially resolved polarization-sensitive imaging.
• Existing THz imaging systems often lack the robustness and efficiency needed for industrial applications.

Purpose of the Study:

• To develop and demonstrate an efficient single-pixel terahertz imaging system for spatially mapping the dichroism of anisotropic fiber distributions in wood.
• To provide a cost-effective and robust alternative to current THz NDE systems for industrial use.
• To enable detailed wood grain inspection through polarization-resolved THz imaging.

Main Methods:

• Implementation of a terahertz single-pixel computational imaging system.
• Utilization of polarizing S-cyclic Hadamard mask patterns (17x19) for spatial encoding of the 0.29 THz beam.
• Acquisition of polarization-resolved THz images of a spruce wood sample at various azimuthal rotations.

Main Results:

• Successful spatial mapping of wood fiber dichroism using the developed THz imaging system.
• Demonstration of durable, inexpensive components and simple optical alignment.
• Acquisition of efficient, polarization-resolved THz images crucial for wood grain inspection.

Conclusions:

• The developed THz single-pixel imager offers an efficient and cost-effective solution for wood NDE.
• The system achieves dichroism analysis accuracy comparable to traditional THz time-domain spectroscopy systems.
• This technology addresses key drawbacks of existing THz inspection systems, paving the way for industrial adoption.