Two-dimensional tomographic terahertz imaging by homodyne self-mixing

Area of Science:

• Optics and Photonics
• Materials Science
• Imaging Techniques

Background:

• Terahertz (THz) imaging offers unique capabilities for non-destructive analysis.
• Compact and efficient THz imaging systems are crucial for practical applications.
• Characterizing powdered materials like α-Lactose monohydrate requires advanced imaging methods.

Purpose of the Study:

• To develop a compact two-dimensional tomographic terahertz imaging system.
• To investigate the use of a single photoconductive antenna (PCA) as both transmitter and receiver.
• To characterize α-Lactose monohydrate powder using THz imaging.

Main Methods:

• Utilized a single photoconductive antenna (PCA) for continuous-wave (CW) terahertz radiation transmission and reception.
• Employed a hollow-core Teflon cylinder filled with α-Lactose monohydrate powder as the sample.
• Implemented homodyne self-mixing (HSM) to extract amplitude and phase information.
• Performed tomographic reconstruction using the Simultaneous Algebraic Reconstruction Technique (SART).
• Modeled refractive effects using ZEMAX software.

Main Results:

• Successfully extracted amplitude and phase information from the HSM signal.
• Demonstrated the ability to identify object geometry and the distribution of α-Lactose monohydrate.
• Analyzed the influence of refraction on the imaging results.
• Achieved tomographic reconstruction at specific THz frequencies, including an absorption line of the powder.

Conclusions:

• The developed compact THz imaging system is effective for characterizing materials.
• A single PCA can efficiently serve as both transmitter and receiver in a THz imaging setup.
• Tomographic reconstruction using SART enables detailed analysis of sample geometry and composition.