Efficient Two-Comb Fourier Spectroscopy
Year: 2008
Type: preprint
Abstract: Molecular fingerprinting through absorption spectroscopy is a powerful analytical method. Light is sent through the analysed medium and its chromatic absorption provides the required information. Fundamental and applied domains benefit from absorption spectroscopy essentially based on laser and Fourier transform spectroscopies. Wide spectral ranges are explored with Doppler-limited resolution. Fast data acquisition, accurate measurements of frequency, intensity, and line shape; time-resolved, selective spectra are achieved with excellent sensitivities. However, presently spectrometers are unable to provide all these features at once. Here we show with experimental evidence that, based on frequency comb lasers, a spectrometer may overcome this difficulty. We have recorded two series of spectra with a 1.5 µm home-made Cr 4+ YAG femtosecond frequency comb. In the first series, we propose to use the comb structure to considerably improve the recording time and signal to noise ratio of Doppler-resolved spectra, which are Fourier transform of the beating signatures of two combs issued from the same initial laser. The second series demonstrates that under very simple experimental conditions, Fourier transform spectroscopists may record much more sensitive spectra, thanks to the brightness of the comb replacing the usual incoherent white light source. Our results show that femtosecond frequency comb spectroscopy is able to provide in a single experiment, multiple species spectra covering at once more than 165 nm with an unapodized resolution equal to 185 MHz. A new detection scheme based on the beating of neighbouring comb lines is proposed to improve the signal to noise ratio. Additionally in a single experiment absorption and dispersion line shapes are measured at once. The final improvement is to reach recording time and resolution at the limit with Fourier spectroscopy based on two independent frequency combs.
Source: arXiv (Cornell University)
Authors: Julien Mandon, G. Guelachvili, N. Picqué
Institution: Université Paris-Sud
Language: English
Subfield: Spectroscopy
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2321484286