Terbium-based fluoride and oxide crystals for visible lasers

In the course of this thesis, Tb3+-doped fluoride and oxide materials have been investigated with regard to their properties as potential laser active materials with emission in the visible range. Main spectroscopic and laser investigations have been carried out in LiLuF4 and LiTbF4, KY3F10 and KTb3F10, BaY2F8, LaF3, and TbF3 as fluorides materials and YAlO3 and TbAlO3, Y3Al5O12, and KY(WO4)2 as oxide materials. The host material plays a fundamental role in the capacity of Tb3+ laser emission as can help to decrease or even avoid detrimental excited state absorption (ESA) processes, unraveling the key to developing efficient Tb3+ lasers. Thus, different Tb3+ materials were investigated for laser experiments, with a wide range of doping concentrations up to stoichiometric 100 at.%. Tb3+ absorption and emission cross-sections were determined by absorption and fluorescence spectroscopy respectively, exposing the feasible wavelength for pumping and laser emission. Measurements of the fluorescence dynamics indicate the lack of interionic processes between Tb3+ ions that could limit the suitable concentration for laser performance. Consequently, high concentrations can contribute to compensate for the low Tb3+ absorption and emission cross-sections. Furthermore, pump-probe ESA measurements show gain in the green and yellow spectral regions for Tb3+ materials, included the oxide YAlO3. This finding is especially relevant as Tb3+ laser emission from an oxide material has not yet been demonstrated. Laser emission with a Tb3+(28 at.%):LiTbF4 crystal was achieved in cw operation, delivering 0.5 W at 587.5 nm with a slope efficiency of 25%, unprecedented values for any direct emitting yellow laser. Diode-pumped laser emission on this crystal was accomplished with a 52% of slope efficiency at 544 nm in the green and a 22% at 587.4 nm in the yellow, entailing the first demonstration of a diode pumped Tb3+-based solid-state laser, to the best of the author’s knowledge. The present work also demonstrates UV-pumping as a viable solution on a Tb3+(14 at.%):LiTbF4 crystal, increasing by two the optical-to-optical efficiency of the overall laser system in comparison with cyan-blue pumping. Laser operation was achieved with Tb3+:BaY2F8 at 581 nm with a slope efficiency of 16%. To the best of the author’s knowledge, this is the first demonstration of laser emission of this crystal.

Author dc:creator

• Castellano Hernández, Elena

Advisor dc:contributor.advisor

• Kränkel, Christian

Licence dc:rights.uri

• https://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Identifier URI

http://dx.doi.org/10.14279/depositonce-15481

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/16703