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UP: Fachverband Umweltphysik

UP 2: Poster Session

UP 2.7: Poster

Dienstag, 9. März 2010, 16:30–18:30, Lichthof

Sensitivity enhancement of an Er³⁺-doped fiber laser to intracavity absorption — •Benjamin Löden, Peter Fjodorow, Klaus Sengstock, and Valeri Baev — Institut für Laserphysik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg

The emission spectrum of a broadband Er³⁺-doped fiber laser is very sensitive to intracavity absorption, which allows extremely sensitive spectroscopy [1]. The highest sensitivity can be achieved with a cw laser and it is limited by nonlinear mode coupling. With a proper choice of laser parameters the nonlinear mode coupling can be reduced allowing highest sensitivities. One of the most important nonlinear mode coupling mechanisms is the spatial inhomogeneity of the gain. It can be reduced by increasing the number of oscillating laser modes using longer laser cavities. With a 2-m-cavity the sensitivity to intracavity absorption is measured to be corresponding to the effective absorption path length of 50 km. The increase of the effective absorption path length over 1000 km is demonstrated with the cavity length of 80 m at low pump rates. Further enhancement of the sensitivity is possible by reducing the mode coupling with the application of a unidirectional ring laser. In this laser the complete elimination of the spatial gain inhomogeneity can be achieved. Besides that a reduction of stimulated Brillouin scattering in the fiber and a decrease of spectral noise is expected. A system with such a high sensitivity can be used for the detection of trace gases and for environmental or medical applications.

[1] A. Goldman, I. Rahinov, S. Cheskis, B. Löhden, S. Wexler, K. Sengstock, V.M. Baev, Chem. Phys. Lett 423, 147 (2006)