Optical-Feedback Cavity-Enhanced Absorption Spectroscopy with a Quantum Cascade Laser.

G. Maisons (1) , P. Gorrotxategi Carbajo (2) , M. Carras (1) , D. Romanini (2, 3)

1 III-V Lab - Alcatel-Thalès III-V lab
2 LSP - Laboratoire de Spectrométrie Physique
3 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]

Optical{feedback cavity{enhanced absorption spectroscopy is demonstrated in the mid{IR using a quantum cascade laser (emitting at 4.46 ¹m). The laser linewidth reduction and frequency locking by selective optical feedback from the resonant cavity ¯eld turns out to be particularly important in this spectral range: It allows strong cavity transmission which compensates for low light sensitivity, especially when using room temperature detectors. We obtain a noise equivalent absorption coe±cient of 3£10¡9 cm¡1, for 1 s averaging of spectra composed by 100 independent points. At 4.46 ¹m this yields a detection limit of 35 pptv for N2O at 50mbar, corresponding to 4£107molecules/cm3, or still to 1 femtomoles in the sample volume.

Domaines: Instrumentations et Détecteurs [physics.ins-det]; Optique [physics.optics]

G. Maisons, P. Gorrotxategi Carbajo, M. Carras, D. Romanini. Optical-Feedback Cavity-Enhanced Absorption Spectroscopy with a Quantum Cascade Laser.. Optics Letters, 2010, 35, pp.3607. ⟨10.1364/OL.35.003607⟩. ⟨hal-00563656⟩