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Stable, tunable, and single-mode operation of an erbium-doped fibre laser system using a saturable absorber for gas spectroscopy applications
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Paper Abstract

We present an erbium doped fibre ring laser system to realize single frequency lasing by incorporating a reflector with ~2m of un-pumped polarization-maintaining erbium-doped fibre to act as a saturable absorber. Depending on the particular requirements, the fibre reflector may be a fibre Bragg grating (FBG), loop mirror (LM) or a reflective coating on the fibre end. In this way, a transient grating is formed in the saturable absorber which acts as a narrow-band optical filter, reducing the number of modes over which the laser can operate and hence suppressing mode hopping in the cavity. Polarization-maintaining (PM) components are used throughout the system, except for the EDFA, and a polarization controller is used for enhancing stability and to ensure that the state of polarization is properly aligned. With this system we have observed a long period of stable, narrow line-width and single mode operation, tuneable over 30nm. The intended application is for gas spectroscopy using wavelength scanning and pump modulation. A Sagnac loop filter (SLF) can be used to scan the centre wavelength over a gas absorption line while the pump modulation produces an amplitude modulated signal on the output, suitable for detection by a lock-in (phase-sensitive) amplifier. The method is useful for the recovery of absorption line-shapes in the near-IR where the overtone absorption lines are weak. Compared with the use of a traditional DFB laser source, the fibre laser offers the advantages of a much broader tuning range and recovery of distortion-free line-shapes since wavelength and amplitude modulation may be performed independently.

Paper Details

Date Published: 19 February 2009
PDF: 10 pages
Proc. SPIE 7195, Fiber Lasers VI: Technology, Systems, and Applications, 719525 (19 February 2009); doi: 10.1117/12.808157
Show Author Affiliations
Norhana Arsad, Univ. of Strathclyde (United Kingdom)
National Univ. of Malaysia (Malaysia)
George Stewart, Univ. of Strathclyde (United Kingdom)


Published in SPIE Proceedings Vol. 7195:
Fiber Lasers VI: Technology, Systems, and Applications
Denis V. Gapontsev; Dahv A. Kliner; Jay W. Dawson; Kanishka Tankala, Editor(s)

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