Fast infrared chemical imaging with a quantum cascade laser

Area of Science:

• Spectroscopy
• Microscopy
• Biomedical Imaging

Background:

• Infrared (IR) spectroscopic imaging visualizes molecular microstructure without dyes.
• Current Fourier transform infrared (FT-IR) imaging is dye-free but slow due to scanning.
• Quantum cascade lasers (QCL) offer high intensity for accelerated IR imaging.

Purpose of the Study:

• To develop a novel discrete frequency IR (DF-IR) spectral imaging microscope.
• To leverage QCLs for high-speed, high-definition IR chemical imaging.
• To compare the performance of the new DF-IR system with established FT-IR methods.

Main Methods:

• Coupled a rapidly tunable QCL with a high-performance microscope and focal plane array (FPA) detector.
• Multiplexed multiple QCLs for broad spectral coverage (776.9–1904.4 cm⁻¹).
• Designed the optical system for high-definition (HD) IR imaging based on theoretical rules.

Main Results:

• Achieved spectral and spatial fidelity comparable to the best FT-IR systems.
• Demonstrated a speedup in achieving equivalent signal-to-noise ratio (SNR) compared to linear array systems.
• Showcased a 3-order of magnitude faster scanning of tissue microarrays (TMA) per spectral frequency.

Conclusions:

• The new DF-IR microscope offers significant speed advantages for IR chemical imaging.
• The system provides high spectral and spatial fidelity for analyzing cells and tissues.
• This technology enables high-throughput molecular microstructure analysis.