Terahertz pulse time-domain holography with balance detection: complex-domain sparse imaging

Area of Science:

• Optics and Photonics
• Terahertz Spectroscopy
• Image Processing

Background:

• Terahertz (THz) pulse time-domain holography is a powerful imaging technique.
• Balance detection systems in THz holography exhibit unique noise characteristics compared to photoconductive antenna systems.
• Understanding and mitigating noise is crucial for high-quality THz imaging.

Purpose of the Study:

• To investigate the noise properties of terahertz pulse time-domain holography with raster scanning using a balance detection system.
• To develop and evaluate advanced filtering algorithms for complex-domain THz images.
• To enhance the dynamic range and image quality in THz holography.

Main Methods:

• Analysis of the Skellam distribution model for noise in balance detection systems.
• Numerical simulations and experimental investigations of the Skellam noise model.
• Application of block-matching algorithms for filtering spatio-temporal and spatiospectral volumetric data.
• Development of a novel 3D cube complex-domain filter algorithm.

Main Results:

• The noise variance in the balance detection system was found to be independent of the true signal.
• A new 3D cube complex-domain filter algorithm was presented, utilizing simultaneous block matching in spatial and frequency coordinates.
• Combining temporal and complex-domain filters significantly expanded the dynamic range for amplitude/phase information retrieval.
• Experimental results demonstrated a marked improvement in image quality in both time and complex-spectral domains.

Conclusions:

• The Skellam distribution model accurately describes noise in balance detection THz holography.
• The developed 3D cube complex-domain filter effectively enhances image quality.
• The combined filtering approach broadens the applicability of terahertz holography for detailed material characterization.