MULTIPLEX MID-IR SPECTROSCOPY WITH Cr$^{2+}$-BASED LASERS
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Date
2006
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
\maketitle Laser operation of Cr$^{2+}$-doped chalcogenides has been demonstrated in the mid-nineties and hasled to a new class of efficient mid-infrared laser crystals. Among them, Cr$^{2+}$:ZnSe and Cr$^{2+}$:ZnS represent interesting alternative to difference frequency generation and semiconductor lasers for spectroscopy. They indeed exhibit} broad tunability in the 2.5 $\mu$m region, high-power room-temperature operation and compactness, especially with fiber or diode lasers pumping.\\ In this paper, we report application of Cr$^{2+}$:ZnSe and Cr$^{2+}$:ZnS lasers to high-resolution and high-sensitivity intracavity absorption spectroscopy (ICLAS) analyzed by time-resolved Fourier transform (TRFT) spectroscopy. ICLAS with an evacuated tunable Cr$^{2+}$: ZnSe laser is performed with a high-resolution TRFT interferometer with a minimum detectable absorption coefficient equal to 4 10$^{-9}$ cm$^{-1}$Hz$^{-1/2}$ around 2500 nm}. This is the extreme limit presently reached in the infrared by ICLAS with Doppler limited resolution. The broad gain band of the crystal allows a spectral coverage at most equal to 125 nm, wide enough to see entire vibration bands. Weak CO$_2$, N$_2$O}$ from long path absorption spectra, submitted for publication, 2006.} and C$_2$H$_2$} bands are observed for the first time in a laboratory and their analysis is discussed. Relatively to Cr$^{2+}$:ZnSe, Cr$^{2+}$:ZnS has a blue-shifted emission, peaking around 2.4 $\mu$m, making it especially attractive for applications in this water-free window of the atmosphere. We report first spectroscopic application}$:ZnS laser-based spectrometer, submitted for publication, 2006.} of a Cr$^{2+}$:ZnS laser. We indeed demonstrate a broadband Cr$^{2+}$:ZnS laser for ICLAS, utilizing Er-fiber or direct diode pumping. Illustration is provided with spectra of weak bands of N$_2$O.
Description
Author Institution: Laboratoire de Photophysique Moleculaire, Unite Propre du C.N.R.S., Batiment 350,; Universite de Paris-Sud, 91405 Orsay, France, email: nathalie.picque@ppm.u-psud.fr ; Institut fur Photonik, TU Wien, Gusshausstr. 27/387, A-1040 Vienna, Austria