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Efficient generation of blue light by frequency doubling of a Nd:YAG laser operating on 4F3/2 → 4I9/2 transitions
KTH, Superseded Departments, Physics.
Acreo AB, Kista.
Acreo AB, Kista.
2003 (English)In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 76, no 2, 135-141 p.Article in journal (Refereed) Published
Abstract [en]

Efficient room-temperature operation of F-4(3/2) --> I-4(9/2) transitions in diode-end-pumped Nd:YAG lasers at 946 nm and 938.5 nm is reported. 7.0-W continuous-wave output power at 946 nm and 3.9 W at 93 8.5 nm have been obtained. An analytical model has been developed for the quasi-three-level laser including the influence of energy-transfer upconversion. Frequency doubling of these transitions in periodically poled KTP generated blue light at 473 nm and 469 nm. Both single-pass extra-cavity as well as intracavity schemes have been investigated.

Place, publisher, year, edition, pages
2003. Vol. 76, no 2, 135-141 p.
Keyword [en]
Continuous wave lasers, Energy transfer, Frequency doublers, Pumping (laser), Frequency doubling, Neodymium lasers
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-8888DOI: 10.1007/s00340-002-1079-1ISI: 000182170800007OAI: oai:DiVA.org:kth-8888DiVA: diva2:14367
Note
QC 20100901Available from: 2005-12-08 Created: 2005-12-08 Last updated: 2010-09-01Bibliographically approved
In thesis
1. Diode-pumped rare-earth-doped quasi-three-level lasers
Open this publication in new window or tab >>Diode-pumped rare-earth-doped quasi-three-level lasers
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many rare-earth-doped materials are suitable for laser operation and this thesis focuses on diode-pumped solid-state lasers employing crystals doped with the trivalent rare-earth ions neodymium (Nd3+), ytterbium (Yb3+) and erbium (Er3+). Especially, the quasi-three-level transitions in Nd and Yb have been studied as well as the eye-safe three-level transition around 1.5 µm in Er.

Quasi-three-level laser transitions in neodymium-doped crystals such as Nd:YAG, Nd:YLF and Nd:YVO4 have received a great deal of interest because they allow for generation of blue light by frequency doubling. For solid-state blue laser sources, there exist numerous applications as in high-density optical data storage, colour displays, submarine communication and biological applications.

Efficient lasing on quasi-three-level transitions at 900¬–950 nm in Nd-doped crystals is considerably more difficult to achieve than on the stronger four-level transitions at 1–1.1 µm. The problems with these quasi-three-level transitions are a significant reabsorption loss at room temperature and a small stimulated emission cross section. This requires a tight focusing of the pump light, which is achieved by end-pumping with high-intensity diode lasers. Nd:YAG lasers at the 946 nm transition have been built and a maximum power of 7.0 W was obtained. By inserting a thin quartz etalon in the laser cavity, the 938.5 nm laser line could be selected and an output power of 3.9 W was then obtained.

By using nonlinear crystals, frequency-doubling of laser light at both 946 nm and 938.5 nm was achieved. Efficient generation of blue light at 473 nm has been obtained in periodically poled KTP, both in single-pass extra-cavity and intracavity configurations. More than 0.5 W was obtained at 473 nm by intracavity doubling. Intracavity second harmonic generation of the 938.5 nm transition gave slightly more than 200 mW at 469 nm.

During recent years, Yb-doped double-tungstate crystals like KGW and KYW have shown efficient laser operation. A comparative, experimental study of the laser performance and thermal-lensing properties between standard b-cut Yb:KGW and Yb:KGW cut along a novel athermal direction is presented. The results show that the thermal lens is about two times weaker and less astigmatic in the athermal-direction-cut crystal, for the same absorbed power. Also, Er-Yb-doped KGW and KYW have been investigated and the fluorescence dynamics have been measured for the Yb (2F5/2), Er (4I13/2) and Er (4S3/2) levels around 1 µm, 1.5 µm and 0.55 µm, respectively.

The influence of upconversion is a detrimental effect both in Nd-doped and Er-Yb-doped lasers. Analytical models starting from rate equations have been developed for these lasers including the influence of upconversion effects. The results of the general models have been applied to 946 nm Nd:YAG lasers and to Er-Yb-doped double-tungstate crystals in order to find the optimum doping concentrations for high gain for an eye-safe laser at 1.53 µm.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. viii, 86 p.
Series
Trita-FYS, ISSN 0280-316X ; 2005:70
Keyword
Optics, laser optics
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-544 (URN)91-7178-220-6 (ISBN)
Public defence
2005-12-16, Sal FD5, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100901Available from: 2005-12-08 Created: 2005-12-08 Last updated: 2010-09-01Bibliographically approved

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