| 1. |
- Bjurshagen, Stefan, et al.
(author)
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Fluorescence dynamics and rate equations analysis in Er3+,Yb3+ doped double tungstates
- 2006
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In: Applied Optics. - 1559-128X .- 2155-3165. ; 45:19, s. 4715-4725
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Journal article (peer-reviewed)abstract
- The fluorescence dynamics in Er3+ and Yb3+ doped KGd(WO4)(2) and KY(WO4)(2) has been investigated. Lifetimes have been measured for the Yb(F-2(5/2)), Er(I-4(13/2)), and Er(S-4(3/2)) levels around 1, 1.5, and 0.55 mu m, respectively. The Yb(F-2(5/2)) lifetimes show a decreasing trend toward the limiting Er(I-4(11/2)) lifetime with increasing Er-to-Yb concentration ratio, whereas the Er(I-4(13/2)) lifetimes are mostly unaffected by the doping concentrations. A rate equation analysis has been performed to explain the observed behavior and gain is calculated for a continuous-wave laser at 1.53 mu m to find the optimum doping concentrations for high gain.
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| 2. |
- Bolanos, Western, et al.
(author)
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Epitaxial layers of KY1-x-yGdxLuy(WO4)(2) doped with Er3+ and Tm3+ for planar waveguide lasers
- 2010
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In: Optical materials (Amsterdam). - : Elsevier BV. - 0925-3467 .- 1873-1252. ; 32:3, s. 469-474
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Journal article (peer-reviewed)abstract
- Here we show the results we obtained in the fabrication of planar wave guide lasers based on monoclinic double tungstates doped with Er3+ and Tm3+. We have successfully introduced these ions into the lattice matched KY0.59Gd0.19Lu0.22(WO4)(2) epitaxial layers grown on KY(WO4)(2) substrates without loss of optical quality and keeping a high refractive index contrast between the epitaxial layer and the substrate. We characterized the waveguiding properties of these epitaxial layers at lambda = 632.8 nm by dark modes spectroscopy, and we showed that these waveguides can support several TE and TM modes. Spectroscopic characterization of the active lanthanide ions in these crystals is also presented.
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| 3. |
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| 4. |
- Loiko, Pavel, et al.
(author)
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Inkjet-printing of graphene saturable absorbers for similar to 2 mu m bulk and waveguide lasers
- 2018
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In: Optical Materials Express. - : Optical Society of America. - 2159-3930 .- 2159-3930. ; 8:9, s. 2803-2814
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Journal article (peer-reviewed)abstract
- A technique for inkjet-printing of graphene saturable absorbers (SAs) for similar to 2-mu m bulk and waveguide lasers is presented. Based on distillation-assisted solvent exchange to fabricate high-concentration graphene inks, this technique is capable of producing few-layer graphene films of arbitrary shape. Absorption saturation of graphene printed on glass is demonstrated at similar to 1.56 mu m for picosecond and femtosecond pulses indicating a large fraction of the saturable losses. Inkjet-printed transmission-type graphene SAs are applied in passively Q-switched nanosecond thulium (Tm) microchip and planar waveguide lasers. The Tm microchip laser generates 136 ns / 1.2 mu J pulses at 1917 nm with a repetition rate of 0.37 MHz with a Q-switching conversion efficiency reaching 65%. The planar waveguide laser generates 98 ns / 21 nJ pulses at 1834 nm at a repetition rate in the MHz-range. The inkjet-printing technique is promising for production of patterned SAs for waveguide lasers.
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| 5. |
- Mena, Josué, et al.
(author)
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Tailoring Wettability Properties of GaN Epitaxial Layers through Surface Porosity Induced during CVD Deposition
- 2021
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 37:50, s. 14622-14627
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Journal article (peer-reviewed)abstract
- Porous GaN epitaxial layers were prepared using single-step chemical vapor deposition (CVD) through the direct reaction of ammonia with gallium. The degree of porosity and pore diameters in the resulting GaN were analyzed by means of SEM and AFM and were found to depend on the GaN deposition time. Furthermore, the evolution of the contact angle of a droplet of water located on the surface of these GaN epitaxial layers with the deposition time was investigated. We observe a transition from the hydrophilic regime to the hydrophobic regime for deposition times longer than 15 min. The observed dependence of GaN hydrophobicity on its degree of porosity is discussed and explained in the framework of the Cassie-Baxter model.
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