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Femtosecond Laser Filaments for Use in Sub-Diffraction-Limited Imaging and Remote Sensing
Published on: April 25, 2019
Femtosecond laser Fourier transform absorption spectroscopy
Julien Mandon1, Guy Guelachvili, Nathalie Picqué
1Laboratoire de Photophysique Moléculaire, CNRS, Université de Paris-Sud, Orsay, France.
Optics Letters
|June 19, 2007
Summary
Femtosecond lasers now serve as broadband infrared sources for high-resolution Fourier transform absorption spectroscopy. This advancement significantly reduces recording times for acetylene spectra, enabling faster, more sensitive molecular analysis.
Area of Science:
- Molecular Spectroscopy
- Laser Physics
- Infrared Spectroscopy
Background:
- High-resolution Fourier transform absorption spectroscopy traditionally relies on conventional broadband sources like tungsten lamps.
- Achieving high signal-to-noise ratios and broad spectral coverage often requires long recording times.
- Acetylene (C2H2) spectroscopy is crucial for understanding molecular dynamics and atmospheric composition.
Purpose of the Study:
- To demonstrate the novel application of a femtosecond mode-locked laser as a broadband infrared source for high-resolution Fourier transform absorption spectroscopy.
- To assess the performance of this laser-based system for recording complex molecular spectra, specifically focusing on acetylene.
- To quantify the improvement in recording time and sensitivity compared to conventional spectroscopic methods.
Main Methods:
- Utilized a Cr(4+):YAG femtosecond mode-locked laser as the broadband infrared source.
- Employed high-resolution Fourier transform absorption spectroscopy to record the spectrum of acetylene.
- Acquired data from acetylene gas passed through a single-pass 80-cm-long cell.
Main Results:
- Successfully recorded the entire nu(1)+nu(3) vibration-rotation band region of acetylene (1480-1600 nm) in 7.9 seconds with a signal-to-noise ratio of 1000.
- Observed hot bands of acetylene and the nu(1)+nu(3) band of the (13)C(12)CH(2) isotopologue simultaneously.
- Achieved a reduction in recording time by approximately 150-fold compared to conventional tungsten lamp sources for similar results.
- Determined a noise equivalent absorption coefficient of 7x10(-7) cm(-1)Hz(-1/2) at 1-second averaging.
Conclusions:
- Femtosecond mode-locked lasers are effective broadband infrared sources for high-resolution Fourier transform absorption spectroscopy.
- This laser-based approach offers a substantial increase in speed and sensitivity for molecular spectral acquisition.
- The technique enables rapid and detailed analysis of complex molecular spectra, including minor isotopologues and hot bands.
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