| 1. |
- Engholm, Magnus, et al.
(author)
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Improved photodarkening resistivity in ytterbium-doped fiber lasers by cerium codoping
- 2009
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In: Optics Letters. - 0146-9592 .- 1539-4794. ; 34:8, s. 1285-1287
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Journal article (peer-reviewed)abstract
- We show that the photodarkening resistivity of ytterbium-doped fiber lasers can be greatly improved by cerium codoping. It is suggested that the coexistence of the redox couple Ce3+⁄Ce4+ in the glass provides means for trapping both hole- and electron-related color centers that are responsible for the induced optical losses in Yb-doped fiber lasers.
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| 2. |
- Feugnet, G., et al.
(author)
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Improved laser-induced fluorescence method for bio-attack early warning detection system
- 2008
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE.
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Conference paper (peer-reviewed)abstract
- Laser Induced Fluorescence (LIF) could permit fast early warning systems either for point or standoff detection if a reliable classification of warfare biological agents versus biological or non-biological fluorescing background can be achieved. In order to improve LIF discrimination capability, a new system is described in which the fluorescence pattern is enriched by the use of multiple wavelength delayed excitation while usual spectral fluorescence analysis is extended to time domain to use both aspects as criteria for classification. General considerations and guidelines for the system design are given as well as results showing good discrimination between background and simulants.
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| 3. |
- Jelger, Pär, et al.
(author)
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A Volume Bragg Grating Locked Nd:fiber Laser
- 2007
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In: 2007 CONFERENCE ON LASERS & ELECTRO-OPTICS/QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (CLEO/QELS 2007). - NEW YORK : IEEE. ; , s. 1946-1947
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Conference paper (peer-reviewed)abstract
- A Neodymium doped LMA fiber is locked with a volume Bragg grating for the first time, and compared to a conventional fiber laser setup. The efficiency is improved and the linewidth is drastically reduced.
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| 4. |
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| 5. |
- Jelger, Pär, et al.
(author)
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An in-fibre microcavity
- 2007
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In: Opt.InfoBase Conf. Papers. - NEW YORK : Optical Society of America. ; , s. 1233-1234
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Conference paper (peer-reviewed)abstract
- A novel all-fiber spliced microcavity for chemical and biological optical studies is described. Its design allows coupling with low loss light from a fiber into a liquid or gas contained in a capillary or PCF.
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| 6. |
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| 7. |
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| 8. |
- Jelger, Pär, et al.
(author)
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Degradation-resistant lasing at 980 nm in a Yb/Ce/Al-doped silica fiber
- 2010
-
In: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 27:2, s. 338-342
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Journal article (peer-reviewed)abstract
- In this work we measure how photodarkening affects the optical efficiency for three different Yb/Al-doped silica fibers operating at 980 nm, one of which is codoped with cerium. A volume Bragg grating is used for linewidth control and added rejection of amplified spontaneous emission. Several hours of degradation-resistant operation is obtained with the Ce-codoped fiber, while for the Yb/Al doped fibers a large drop in efficiency is observed within the first hour of operation. Our results show that Yb/Ce/Al-doped fibers could be excellent candidates for high-power 980 nm fiber laser sources.
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| 9. |
- Jelger, Pär, et al.
(author)
-
Efficient narrow-linewidth volume-Bragg grating-locked Nd : fiber laser
- 2007
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In: Optics Express. - 1094-4087. ; 15:18, s. 11336-11340
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Journal article (peer-reviewed)abstract
- A neodymium doped microstructured large mode area fiber is frequency locked with a volume Bragg grating. This configuration is compared with a conventional fiber laser setup. A high efficiency (51% slope), stable output and a drastically narrowed linewidth (<0.07nm) are achieved.
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| 10. |
- Jelger, Pär, et al.
(author)
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Efficient skew-angle cladding-pumped tunable narrow-linewidth Yb-doped fiber laser
- 2007
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In: Optics Letters. - 0146-9592 .- 1539-4794. ; 32:24, s. 3501-3503
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Journal article (peer-reviewed)abstract
- A skew-angle cladding-pumped tunable Yb-doped fiber laser is presented. The laser was tunable over more than 30 nm, from 1022 to 1055 nm, by employing a volume Bragg grating in a retroreflector configuration as one of the cavity delimiters. Output powers in excess of 4.3 W were recorded with a spectral bandwidth of 5 GHz and an M2 value below 1.3 over the whole tuning range.
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| 11. |
- Jelger, Pär, 1978-
(author)
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High Performance Fiber Lasers with Spectral, Thermal and Life Time Control
- 2009
-
Doctoral thesis (other academic/artistic)abstract
- 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.
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| 12. |
- Jelger, Pär, et al.
(author)
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High-power linearly-polarized operation of a cladding-pumped Yb fibre laser using a volume Bragg grating for wavelength selection
- 2008
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In: Optics Express. - 1094-4087. ; 16:13, s. 9507-9512
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Journal article (peer-reviewed)abstract
- In this work a volume Bragg grating is used as a wavelength selective element in a high-power cladding-pumped Yb-doped silica fiber laser. The laser produced 138 W of linearly-polarized single-spatial-mode output at 1066 nm with a relatively narrow linewidth of 0.2 nm for similar to 202 W of launched pump power at 976 nm. The beam propagation factor (M-2) for the output beam was determined to be 1.07. Thermal limitations of volume Bragg gratings are discussed in the context of power scaling for fiber lasers.
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| 13. |
- Jelger, Pär, et al.
(author)
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Highly efficient temporally stable narrow linewidth cryogenically cooled Yb-fiber laser
- 2009
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In: Optics Express. - 1094-4087. ; 17:10, s. 8433-8438
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Journal article (peer-reviewed)abstract
- Cryogenic cooling is an effective way of increasing the efficiency in many solid-state lasers. In fiber lasers however, while the efficiency is increased, a reduced reabsorption in combination with reduced homogeneous broadening tends to broaden the linewidth, yielding a low spectral power density of the laser emission. In this work we lock a cryogenically-cooled Yb-doped fiber laser with a volume Bragg grating to overcome this problem and achieve a temporally stable narrow linewidth highly efficient laser. We extract 11.4-W of output power in spectral window of less than 0.4-nm with 14.5-W of launched pump light.
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| 14. |
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| 15. |
- Jelger, Pär, et al.
(author)
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Narrow linewidth dual volume-bragg-grating locked ytterbium-doped fiber-laser
- 2009
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In: Advanced Solid-State Photonics (ASSP) 2009. - Washington, D.C. : Optical Society of America. - 9781557528643
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Conference paper (peer-reviewed)abstract
- Two identical highly reflective volume Bragg gratings are used in tandem to lock an ytterbium doped fiber laser. A narrow linewidth (<2GHz) and high efficiency (>70%) is achieved with output powers above 7W.
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| 16. |
- Jelger, Pär, et al.
(author)
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Narrow linewidth high output-coupling dual VBG-locked Yb-doped fiber laser
- 2010
-
In: Optics Express. - 1094-4087. ; 18:5, s. 4980-4985
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Journal article (peer-reviewed)abstract
- 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.
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| 17. |
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| 18. |
- Jelger, Pär, et al.
(author)
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Spectral Narrowing of Highly Efficient Cryogenically Cooled Ytterbium Doped Fiber Lasers
- 2009
-
In: 2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum Electronics and Laser Science Conference, CLEO/QELS 2009. - Washington, D.C. : IEEE. - 9781557528698 ; , s. 994-995
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Conference paper (peer-reviewed)abstract
- VBGs can efficiently be used to mitigate the spectrally broad output from cryogenically cooled Yb-fiber lasers. We extract 11.5-W of output power in spectral window of less than 0.4-nm with 14.5-W of launched pump light.
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| 19. |
- Jelger, Pär, et al.
(author)
-
Volume bragg grating tuned large mode area fiber laser
- 2008
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In: Adv Solid-State Photon. - Washington, D.C. : OSA. - 1557528500 - 9781557528506
-
Conference paper (peer-reviewed)abstract
- A narrow linewidth ytterbium-doped large-mode area VBG-tuned fiber laser is demonstrated. The output power was >4.3W (77% slope efficiency) and the tuning range was 33 nm (5 GHz linewidth) with nearly diffraction limited output (M2<1.3).
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| 20. |
- Jonsson, P., et al.
(author)
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Spectral detection of ultraviolet laser induced fluorescence from individual bioaerosol particles
- 2006
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In: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 0819464961 - 9780819464965 ; 6398
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Journal article (peer-reviewed)abstract
- We present results of a measurement system designed for detecting the fluorescence spectrum of individual aerosol particles of biological warfare agents excited with laser pulses at wavelengths around 290 or 340 nm. The biological aerosol is prepared and directed into a narrow air beam. A red laser is focused on the aerosol beam and a trigger photomultiplier tube monitor the presence of individual particles by measuring the scattered light. When a particle is present in the detection volume, a laser pulse is triggered from an ultraviolet laser and the fluorescence spectrum is acquired with a spectrometer based on a diffraction grating and a 32 channels photomultiplier tube array with single-photon sensitivity. The spectrometer measures the fluorescence spectra in the wavelength region from 300 to 800 nm. In the experiment we used different simulants of biological warfare agents. These bioaerosol particles were excited by a commercial available gas laser (337 nm), or a laser (290 nm) that we have developed based on an optical parametric oscillator with intracavity sum-frequency mixing. In the analysis of the experiments we compare the measured signals (fluorescence spectra, total fluorescence energy and the scattered energy) from the individual bioaerosol particles excited with the two different ultraviolet wavelengths.
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| 21. |
- Kim, J. W., et al.
(author)
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High-power and wavelength-tunable operation of an Er, Yb fiber laser using a volume Bragg grating
- 2008
-
In: Optics Letters. - 0146-9592 .- 1539-4794. ; 33:11, s. 1204-
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Journal article (peer-reviewed)abstract
- Efficient high-power operation of double-clad Er,Yb-doped fiber lasers with fixed-wavelength and wavelength-tunable resonator configurations using volume Bragg gratings for wavelength selection are reported. The fixed-wavelength laser yielded a maximum output power of 103 W at 1552.6 nm with a linewidth of ∼0.4 nm (FWHM) for a launched pump power of 290 W at 976 nm. The wavelength-tunable laser could be tuned from 1528 to 1550 nm with a linewidth of 0.2 nm (FWHM) and with output power in the range 30-38 W for a launched pump power of 120 W. The prospects for further improvement in performance are considered.
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| 22. |
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| 23. |
- Laurell, Fredrik, et al.
(author)
-
Applications of volume bragg gratings in high-power fiber lasers
- 2010
-
In: Optics InfoBase Conference Papers. - Washington, D.C. : Optical Society of America (OSA). ; , s. 5465515-
-
Conference paper (peer-reviewed)abstract
- In this presentation the latest results on volume Bragg grating locked fiber lasers will be reviewed. This novel technique provides one to two orders of magnitude improved spectral brightness, improved temporal stability and at least equally efficient lasing as when ordinary dielectric mirrors are used. Results on tuning and photodarkening resistant fiber lasers are also presented, as well as some results where the lasers are used in nonlinear optics.
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| 24. |
- Malmström, Mikael, et al.
(author)
-
Photodarkening resistant Yb/Ce/Al silica 980 nm fiberlaser
- 2010
-
In: Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference. - Washington, D.C. : IEEE. - 9781557528902 ; , s. 5500412-
-
Conference paper (peer-reviewed)abstract
- A linearly polarized fiber laser emitting at 979 nm with an output power of 2 W is presented. By using a photodarkening-resistant Yb/Ce/Al-codoped silica fiber, degradation-free operation is achieved over several hours.
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| 25. |
- Seger, Kai, et al.
(author)
-
Tunable and Passively Q-Switched Nd:YVO4 Laser Using a Chirped Volume Bragg Grating
- 2009
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In: 2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum Electronics and Laser Science Conference, CLEO/QELS 2009. - Washington, D.C. : IEEE. - 9781557528698 ; , s. 1523-1524
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Conference paper (peer-reviewed)abstract
- A Nd:YVO4 laser was locked with a chirped volume Bragg grating. Tuning was performed from 1063nm to 1065nm by grating translation with 4W maximum output power. With Cr:YAG, Q-switched pulses with 17ns, 8 mu J were achieved.
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