Noise-immune cavity-enhanced optical frequency comb spectroscopy: a sensitive technique for high-resolution broadband molecular detection
2015 (English)In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 119, no 1, 87-96 p.Article in journal (Refereed) PublishedText
Noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS) is a recently developed technique that utilizes phase modulation to obtain immunity to frequency-to-amplitude noise conversion by the cavity modes and yields high absorption sensitivity over a broad spectral range. We describe the principles of the technique and discuss possible comb-cavity matching solutions. We present a theoretical description of NICE-OFCS signals detected with a Fourier transform spectrometer (FTS) and validate the model by comparing it to experimental CO2 spectra around 1,575 nm. Our system is based on an Er:fiber femtosecond laser locked to a cavity and phase-modulated at a frequency equal to a multiple of the cavity free spectral range (FSR). The NICE-OFCS signal is detected by a fast-scanning FTS equipped with a high-bandwidth commercial detector. We demonstrate a simple method of passive locking of the modulation frequency to the cavity FSR that significantly improves the long-term stability of the system, allowing averaging times on the order of minutes. Using a cavity with a finesse of ~9,000, we obtain absorption sensitivity of 6.4 × 10−11 cm−1 Hz−1∕2 per spectral element and concentration detection limit for CO2 of 450 ppb Hz−1/2, determined by multiline fitting.
Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2015. Vol. 119, no 1, 87-96 p.
IdentifiersURN: urn:nbn:se:umu:diva-114664DOI: 10.1007/s00340-015-6010-7ISI: 000352292500011OAI: oai:DiVA.org:umu-114664DiVA: diva2:897424
FunderCarl Tryggers foundation , CTS12:131Swedish Research Council, 621-2012-3650Swedish Foundation for Strategic Research , ICA12-0031
This project was supported by the Swedish Research Council (621-2012-3650), Swedish Foundation for Strategic Research (ICA12-0031), the Carl Trygger’s Foundation (CTS12:131), and the Faculty of Science and Technology, Umeå University.2016-01-252016-01-252016-03-21Bibliographically approved