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Related Concept Videos

Total Internal Reflection Fluorescence Microscopy01:05

Total Internal Reflection Fluorescence Microscopy

Total internal reflection fluorescence microscopy or TIRF is an advanced microscopic technique used to visualize fluorophores in samples close to a solid surface with a higher refractive index, such as a glass coverslip. TIRF only allows fluorophores in proximity to the solid surface to be excited. When light from a medium with a lower refractive index (such as air) hits the glass coverslip at a critical angle, the light undergoes total internal reflection stead of passing through the glass.

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Simulation, Fabrication and Characterization of THz Metamaterial Absorbers
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Absorption-sensitive diffuse reflection imaging of concealed powders using a terahertz quantum cascade laser.

Paul Dean1, Muhammad U Shaukat, Suraj P Khanna

  • 1School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK. p.dean@leeds.ac.uk

Optics Express
|June 12, 2008
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Summary

This study demonstrates terahertz imaging for detecting hidden powders using a quantum cascade laser. The technique analyzes sub-surface absorption for material identification in reflection, showing promise for concealed substance detection.

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Area of Science:

  • Terahertz spectroscopy and imaging
  • Materials science
  • Non-destructive testing

Background:

  • Terahertz (THz) imaging offers unique capabilities for non-destructive analysis of materials.
  • Detecting concealed powders often requires advanced sensing techniques for security and quality control.

Purpose of the Study:

  • To demonstrate diffuse reflection imaging in air for concealed powdered samples using a terahertz quantum cascade laser.
  • To validate the sensitivity of the detection scheme to sub-surface absorption.
  • To extract material properties, specifically the absorption coefficient, from scattering data.

Main Methods:

  • Utilized a terahertz quantum cascade laser for diffuse reflection imaging.
  • Employed characterized powder admixtures of polystyrene and polymethyl methacrylate (PMMA).
  • Applied Kubelka-Munk scattering theory and quasi-crystalline approximation models to backscattering intensity data.

Main Results:

  • Confirmed the sensitivity of the THz imaging scheme to sub-surface absorption.
  • Successfully extracted the absorption coefficient of PMMA from the measured data.
  • Demonstrated high-resolution frequency-domain terahertz imaging in a reflection geometry.

Conclusions:

  • High-resolution frequency-domain terahertz imaging is feasible for detecting and identifying concealed powders.
  • The reflection geometry approach is effective for sub-surface analysis.
  • This technique has potential applications in security screening and material characterization.