Investigations on Practical Issues in Solid Immersion Lens Based Sub-Wavelength Terahertz Imaging Technique: System...

Area of Science:

• Optics and Photonics
• Imaging Science

Background:

• Terahertz (THz) imaging offers potential for non-destructive testing, biological sensing, and security.
• Practical implementation of THz imaging systems faces challenges with system stability and image artifacts like fringe patterns.

Purpose of the Study:

• To investigate practical issues in THz imaging systems utilizing a solid immersion lens (SIL).
• To enhance the resolution and overcome limitations of conventional THz imaging techniques.

Main Methods:

• Experimental verification of system stability concerning longitudinal misalignment of the SIL.
• Analytical study of fringe pattern origins in continuous-wave THz imaging.
• Development and application of a phase-shifting method to minimize interference patterns.

Main Results:

• Sub-wavelength beam size (0.7 λ) is maintained within the objective lens's depth-of-focus (~13 λ) despite SIL misalignment.
• A novel method combining two THz images (λ/4 separation) significantly reduces fringe patterns.
• The proposed method successfully images objects with diverse surface profiles, demonstrating broad applicability.

Conclusions:

• Inserting a SIL enhances THz imaging resolution with high tolerance to longitudinal misalignment.
• The developed phase-shifting technique effectively minimizes interference, revealing hidden information and enabling THz imaging for varied surface topographies.