Mid-infrared hyperspectral single-pixel microscopy with a quantum cascade laser.

Area of Science:

• Optics and Photonics
• Spectroscopy
• Materials Science

Background:

• Hyperspectral imaging provides detailed chemical information by capturing spectral data across spatial dimensions.
• Mid-infrared (MIR) microscopy is crucial for analyzing molecular vibrations and chemical compositions.
• Single-pixel imaging (SPI) offers a potential alternative to traditional focal-plane array detectors for spectral imaging.

Purpose of the Study:

• To demonstrate a novel hyperspectral mid-infrared (MIR) microscope system.
• To integrate single-pixel imaging (SPI) technology with a tunable MIR quantum cascade laser (QCL).
• To evaluate the performance and chemical analysis capabilities of the developed SPI-based MIR microscope.

Main Methods:

• Development of a MIR microscope system incorporating a tunable MIR QCL (8.3–11.1 µm) and a digital micromirror device (DMD) for spatial light modulation.
• Experimental analysis of diffraction patterns on the DMD to optimize optical configuration and achieve high modulation contrast for SPI.
• Evaluation of spatial resolution using a reflective test target and spectral validation by characterizing polypropylene (PP) foil and a polymer multilayer section, comparing with Fourier-transform infrared (FTIR) spectra.

Main Results:

• The developed SPI-based MIR microscope achieved a spatial resolution exceeding 24.8 µm at a 10.1 µm wavelength.
• Obtained hyperspectral data, limited to a 9.80–10.42 µm bandwidth due to aperture constraints, successfully identified polypropylene.
• The system demonstrated high modulation contrast, critical for effective SPI performance.

Conclusions:

• The demonstrated hyperspectral MIR microscope effectively utilizes SPI technology for chemical analysis.
• The system offers a promising approach for rapid and efficient hyperspectral IR imaging.
• Further optimization could expand the spectral bandwidth and enhance resolution for broader applications.