Comb-resolved spectroscopy with immersion grating in long-wave infrared.

Area of Science:

• Spectroscopy
• Infrared Technology
• Analytical Chemistry

Background:

• Direct frequency comb spectroscopy (FCS) offers high resolution but is challenging in the long-wave infrared (LWIR) region.
• Existing LWIR spectrometers lack the necessary resolution for detailed molecular analysis of complex samples.

Purpose of the Study:

• To develop a novel dispersive spectrometer for high-resolution direct frequency comb spectroscopy in the 8-10 μm LWIR region.
• To demonstrate the capability of this spectrometer for resolving individual comb modes and analyzing molecular spectra.

Main Methods:

• Utilized a compact immersion grating within a dispersive spectrometer setup.
• Employed cavity filtering for individual comb mode-resolved imaging.
• Applied the system to acquire spectra of simple and complex molecules.

Main Results:

• Achieved a frequency resolution of 460 MHz, the highest reported for a dispersive spectrometer in the 8-10 μm region.
• Successfully demonstrated mode-resolved imaging and spectral acquisition of various molecular samples.
• Validated the effectiveness of the immersion grating for LWIR spectroscopy.

Conclusions:

• The developed immersion grating spectrometer represents a significant advancement for sensitive, high-resolution spectroscopy in the LWIR.
• This technology is well-suited for analyzing transient, large, or complex molecules, especially when combined with cavity enhancement and cooling.
• Paves the way for new applications in molecular characterization and analysis.