Metrics for spectral and spatial performance in terahertz spectroscopic imaging

Area of Science:

• Terahertz (THz) spectroscopy and imaging
• Optical physics and material characterization

Background:

• Broadband material characterization in spectroscopy often conflicts with high spatial resolution imaging.
• Terahertz (THz) technology offers unique capabilities for non-destructive analysis.

Purpose of the Study:

• To investigate the trade-offs between spectral and spatial performance in coupled THz microjets and apertures.
• To characterize lactose using THz spectroscopy with varying aperture sizes.

Main Methods:

• Utilized terahertz time-domain spectroscopy (THz-TDS) to analyze lactose transmission through apertures of 1000, 500, and 250 µm.
• Evaluated spectral performance using Kramers-Kronig error and spectral cutoff frequency.
• Assessed imaging performance via modulation depth and spatial resolution at different THz frequencies (0.3-0.9 THz).

Main Results:

• Apertures function as high-pass filters, enhancing spectral accuracy at higher frequencies.
• Spectral cutoff frequencies were observed at <0.3 THz, 0.41 THz, and 0.84 THz for the respective aperture widths.
• Spatial resolutions of 1000 µm, 250 µm, and 250 µm were achieved at 0.3 THz, 0.6 THz, and 0.9 THz, respectively.

Conclusions:

• Optimizing terahertz spectroscopic imaging requires a simultaneous consideration of both spectral and spatial performance metrics.
• Aperture design critically influences the balance between spectral accuracy and spatial resolution in THz imaging systems.