Ultraviolet Raman Wide-Field Hyperspectral Imaging Spectrometer for Standoff Trace Explosive Detection

Area of Science:

• Spectroscopy
• Materials Science
• Analytical Chemistry

Background:

• Raman spectroscopy is a powerful technique for chemical identification.
• Deep UV excitation offers unique advantages for certain analytes.
• Standoff detection capabilities are crucial for security applications.

Purpose of the Study:

• To develop the first deep ultraviolet (UV) Raman standoff wide-field imaging spectrometer.
• To utilize photonic crystals for selective spectral region detection in the deep UV range.
• To demonstrate the system's capability for detecting energetic materials.

Main Methods:

• Fabrication of a photonic crystal using self-assembled silica nanoparticles (35.5 ± 2.9 nm).
• Utilizing the photonic crystal's Bragg diffraction to isolate narrow UV spectral regions (∼1.0 nm FWHM).
• Angle tuning the photonic crystal to select specific Raman spectral bands of pentaerythritol tetranitrate (PETN) and ammonium nitrate (AN).

Main Results:

• Successful construction and operation of a deep UV Raman standoff imaging spectrometer.
• Demonstrated detection of PETN and AN samples (∼10-1000 µg/cm²) at 2.3 m standoff distance using 229 nm excitation.
• Estimated detection limits of approximately 1 µg/cm² for PETN and AN films.

Conclusions:

• The developed photonic crystal-based deep UV Raman spectrometer is a novel and effective tool for standoff detection.
• The system shows promise for rapid, sensitive identification of energetic materials in various scenarios.
• Further optimization could enhance detection limits and expand the range of detectable analytes.