Ultra-broadband spectroscopy using a 2-11.5 µm IDFG-based supercontinuum source

Area of Science:

• Spectroscopy
• Laser Physics
• Environmental Science

Background:

• Intrapulse difference frequency generation (IDFG) supercontinuum sources offer novel capabilities for mid-infrared (mid-IR) gas spectroscopy.
• These sources provide high power, broad spectral coverage (2-11.5 µm), and low relative intensity noise, ideal for the molecular fingerprint region.

Purpose of the Study:

• To demonstrate the performance of an IDFG-based supercontinuum source coupled with a multipass cell and Fourier transform spectrometer (FTS) for multispecies trace gas detection.
• To evaluate the system's sensitivity and applicability in real-world environmental and biological monitoring scenarios.

Main Methods:

• Utilized a mode-locked laser-based IDFG supercontinuum source generating a 2-11.5 µm spectrum with ~3 W output power.
• Integrated the light source with a multipass gas cell and a custom-built Fourier transform spectrometer (FTS).
• Applied the system to detect various trace gases, including hydrocarbons, oxides, and organic molecules, and analyzed bioreactor off-gas.

Main Results:

• Achieved sub-ppb sensitivity for multiple trace gases (CH4, C2H4, SO2, NOx, acetone, ethyl acetate) within seconds to minutes.
• The supercontinuum source demonstrated superior performance over existing mid-IR sources in noise, spectral coverage, and output power.
• Successfully measured simultaneous concentrations of multiple nitrogen oxides (NO, NO2, N2O) in a bioreactor off-gas sample.

Conclusions:

• The demonstrated spectroscopic system, powered by an IDFG supercontinuum source, offers a robust and sensitive platform for multispecies trace gas analysis.
• Its capabilities are well-suited for diverse applications in environmental monitoring and biological process analysis.
• The system's performance highlights the potential of advanced laser-based spectroscopy for complex gas mixture characterization.