Design and implementation of a Fourier transform spectrometer with a broadband optical frequency comb

Area of Science:

• Spectroscopy
• Laser Physics
• Analytical Chemistry

Background:

• Fourier transform spectroscopy (FTS) is a powerful technique for molecular analysis.
• Traditional FTS systems can be limited by mechanical stability and signal-to-noise ratio.
• Femtosecond laser frequency combs (FCs) offer precise frequency control and broad bandwidth.

Purpose of the Study:

• To develop and validate a novel femtosecond laser frequency comb-based continuous scanning Fourier transform spectrometer (FC-FTS).
• To achieve high spectral resolution and broad tunable wavelength range for gas phase molecule spectroscopy.
• To demonstrate the system's capability for accurate multispecies quantification.

Main Methods:

• Utilized a homemade broadband mid-infrared femtosecond laser frequency comb (FC) and a He:Ne laser for interferogram sampling.
• Implemented real-time correction and optical path difference (OPD) resampling using zero-crossing analysis of the reference signal.
• Employed software-based filtering, autobalancing, and etalon suppression to enhance signal-to-noise ratio.

Main Results:

• Achieved a spectral resolution of 0.06 cm⁻¹ in the 2900–4600 nm wavelength range.
• Improved signal-to-noise ratio by nearly two orders of magnitude through advanced software processing.
• Successfully recorded and analyzed absorption spectra of acetylene, carbonyl sulfide, methane, and water.

Conclusions:

• The developed FC-FTS system provides high-resolution, multispecies quantification capabilities.
• The system is validated for molecular fingerprinting and precise identification of trace components.
• This diagnostic system advances the analysis of complex molecular systems.