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Narrow linewidth high output-coupling dual VBG-locked Yb-doped fiber laser
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.ORCID iD: 0000-0002-2508-391X
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.ORCID iD: 0000-0001-7688-1367
2010 (English)In: Optics Express, ISSN 1094-4087, Vol. 18, no 5, 4980-4985 p.Article in journal (Refereed) Published
Abstract [en]

Two equal highly reflective volume Bragg gratings (VBGs) were used to lock an Yb-doped fiber laser. By heating one of the VBGs, its center wavelength was shifted and the laser was locked on the overlap between the main peak of one grating and the side-lobe of the other creating a large outcoupling with high spectral selectivity. With this simple arrangement, unidirectional output is achieved with a narrow linewidth (2.5GHz), high efficiency (>70%) and with an output power above 7W.

Place, publisher, year, edition, pages
2010. Vol. 18, no 5, 4980-4985 p.
Keyword [en]
Center wavelength; High efficiency; High output; Narrow-line width; Output power; Side lobes; Spectral selectivity; Volume Bragg gratings; Yb-doped fiber lasers
National Category
Atom and Molecular Physics and Optics
URN: urn:nbn:se:kth:diva-14161DOI: 10.1364/OE.18.004980ISI: 000275454100061ScopusID: 2-s2.0-77749304289OAI: diva2:331167
QC 20100721Available from: 2010-07-21 Created: 2010-07-21 Last updated: 2015-03-30Bibliographically approved
In thesis
1. High Performance Fiber Lasers with Spectral, Thermal and Life Time Control
Open this publication in new window or tab >>High Performance Fiber Lasers with Spectral, Thermal and Life Time Control
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis contains the results of research in the fields of spectral control, efficiency andlifetime of high-power, rare-earth doped fiber lasers, properties which are of greatimportance for scientific and industrial applications. Volume Bragg gratings (VBGs) has forthe first time been used together with fiber lasers and the laser performance in terms ofspectral purity, thermal stability, and tunability was evaluated. It was found that VBGs arean excellent high-contrast spectral filter for many fiber laser designs where bulk optics arenecessary, or for speciality fibers such as photonic crystal fibers or large-mode area fibers. Itis also shown that they work equally well in low power and very high-power configurations,i.e. for fiber lasers ranging three orders of magnitude in output power, from ~100 mW to >100 W. Furthermore, VBGs are shown to work very well as tunable spectral filters,producing a narrow emission linewidth in a compact setup.

Concerning efficiency, it was shown how cryogenic cooling of the fiber gain-mediasubstantially increased the efficiency. The reasons are an increased pump absorption, anincreased gain cross-section, and a decreased threshold. The broad spectral output resultingfrom the low temperatures is shown to be easily mitigated by implementing a VBG as oneof the cavity mirrors. The low operating temperature is also shown to efficiently suppressself-pulsing in the fiber laser, which, if left unchecked, can lead to catastrophic break-downof the fiber end-faces. The increased absorption and suppressed self-pulsing allowed a fiberlength long enough to almost completely absorb the pump, which meant that, for the samepump power, more than 60 % higher output-power was attained.

Finally, the lifetime issue of Yb-doped fiber lasers was addressed. It was found that Cecodopingsubstantially reduced the photodarkening-rate while leaving other fiber parametersessentially unchanged. This is especially important for Yb-doped fiber lasers emitting at 980nm, as the high inversion required make them very susceptible to photodarkening. It wasshown that the output power in Yb-doped fiber lasers degraded quickly when no Cecodopingwas present and, conversely, with the right Yb/Ce-codoping ratio, degradationfreelasing could be achieved for many hours.

The research results obtained in this work could be of great interest to scientists andengineers working with spectroscopy, display systems, non-linear optics to just name a fewexamples.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. x, 72 p.
Trita-FYS, ISSN 0280-316X ; 2009:65
National Category
Atom and Molecular Physics and Optics
urn:nbn:se:kth:diva-11711 (URN)978-91-7415-504-4 (ISBN)
Public defence
2009-12-11, Sal FB52, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:00 (English)
QC 20100721Available from: 2009-12-07 Created: 2009-12-07 Last updated: 2015-03-30Bibliographically approved

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