Fast Fourier transform spectroscopy with broadband strongly modulated quantum cascade lasers

• Published in: Applied physics letters Vol. 125; no. 13
• Main Authors: Cargioli, A., Piciocchi, D., Bertrand, M., Faist, J., Scalari, G.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 23-09-2024
• Subjects: Broadband; Delay lines; Fast Fourier transformations; Figure of merit; Quantum cascade lasers; Rotational spectra
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0226044

The combination of speed and resolution is a fundamental figure of merit for Fourier transform spectroscopy. Here, we show that, by combining a fast rotational delay line with a strongly modulated quantum cascade laser (QCL), it is possible to perform broadband spectroscopy over a range of 175 cm−1, with a total effective integration time of about 6 s and a resolution of 0.03 cm−1. Remarkably, even though the resolution of the measurement is limited by the source, the interleaving technique can still be applied when the QCL is not in a frequency comb regime, considerably broadening the bandwidth of the instrument.