Characterising energy transfer upconversion in Nd-doped vanadates at elevated temperatures.

The Energy Transfer Upconversion (ETU) macroparameter is measured for Nd-doped GdVO4 and YVO4 samples at temperatures ranging from Room Temperature (RT) to 450K, by means of a simple and automated z-scan technique. Furthermore, the ground state absorption cross section into the 2H9/2 +4F5/2 energy levels is characterised for both crystals over the same range of temperatures. The 808 nm π-polarisation absorption cross section is found to decrease from (58.6 ± 0.2) pm2 to (30.9 ± 0.6) pm2 for Nd:YVO4 and (54.0 ± 0.3) pm2 to (25.7 ± 0.5) pm2 for Nd:GdVO4, from RT to 450K. Over the same range the ETU coefficient decreases from (3.2 ± 0.7) 10-16cm3/s to (1.8 ± 0.4 10-16cm3/s and (5.0 ± 0.5) 10-16cm3/s to (3.4±0.2) 10-16cm3/s for 0.6 at. % and 1 at. % Nd:YVO4 respectively, and (3.3 ± 0.5) 10-16cm3/s to (0.8 ± 0.2) 10-16cm3/s and (5.5 ± 0.5) 10-16cm3/s to (3.1 ± 0.3) 10-16cm3/s for 0.5 at.% and 1.1 at.% Nd:GdVO4.

Amplification of a radially polarised beam in an Yb:YAG thin-slab.

The use of an Yb:YAG thin-slab architecture for amplification of a radially polarised beam at 1030 nm is investigated and shown to be a promising route for power scaling. The detrimental impact of the Gouy phase shift on radial polarisation purity is considered and a simple scheme for effective phase shift management to restore polarisation purity is presented. Preliminary experiments based on a double-pass amplifier configuration yielded an output beam with a high radial polarisation extinction ratio of 15 dB and no degradation in polarisation purity despite the non- axial symmetry of amplifier gain medium. At 50 W of launched pump power a small-signal gain of 7.5 dB was obtained for a 25 mW input, whilst 4.4 dB gain was obtained for a 1.45 W input. The prospects for further power scaling are discussed.

Compact, highly efficient ytterbium doped bismuthate glass waveguide laser.

Laser slope efficiencies close to the quantum defect limit and in excess of 78% have been obtained from an ultrafast laser inscribed buried channel waveguide fabricated in a ytterbium-doped bismuthate glass. The simultaneous achievement of low propagation losses and preservation of the fluorescence properties of ytterbium ions is the basis of the outstanding laser performance.

Strain field manipulation in ultrafast laser inscribed BiB3O6 optical waveguides for nonlinear applications.

A novel technique was used to control the spatial overlap of the orthogonal linearly polarized waveguide modes in ultrafast laser inscribed BiB(3)O(6) waveguides. We report that the strain fields induced by the expansion of material in the laser focus can be considered independently in the design of "type II" waveguides guiding orthogonal linearly polarized light. The waveguide with the optimal mode overlap was used for type I birefringently phase-matched second-harmonic generation of a continuous wave laser source at 1047 nm.

Ultrafast laser inscription of near-infrared waveguides in polycrystalline ZnSe.

We report the successful fabrication of a low-loss near-IR waveguide in polycrystalline ZnSe using ultrafast laser inscription. The waveguide, which was inscribed using the multiscan fabrication technique, supported a well-confined mode at 1.55 µm. Propagation losses were characterized at 1.55 µm using the Fabry-Perot technique and found to be 1.07 dB · cm(-1) ± 0.03 dB · cm(-1).

The molecular cloning of the complementary deoxyribonucleic acid for bovine vitamin D-dependent calcium-binding protein: structure of the full-length protein and evidence for homologies with other calcium-binding proteins of the troponin-C superfamily of proteins.

We have cloned the cDNA for bovine intestinal vitamin D-dependent calcium-binding protein and, based on the sequence of the DNA, have deduced the structure of the full-length protein. The sequence of the cDNA clone predicts a protein comprised of 78 amino acids with a mol wt of 8788. The mRNA for the protein in bovine duodenum is about 500-600 bases in length. The protein sequence of bovine intestinal calcium-binding protein is 87% homologous with the sequence of porcine intestinal vitamin D-dependent calcium-binding protein and 81% homologous with the sequence of rat intestinal vitamin D-dependent calcium-binding protein. Hydrophilicity plots of the proteins noted above show that despite differences in amino acid sequence the proteins have similar patterns. In addition, the predicted secondary structure of the proteins is similar. Bovine intestinal calcium-binding protein shows 48.6% homology with the alpha-chain and 38.2% homology with the beta-chain of bovine S-100 protein and a similar high degree of homology with the beta-chain of human S-100 protein. The protein also demonstrates 36-43% homology with parvalbumin alpha and beta from various species and with troponin-C. There is some homology with the 28K vitamin D-dependent calcium-binding proteins. Vitamin D-dependent bovine intestinal calcium-binding protein is closely related to other mammalian intestinal calcium-binding proteins and to the S-100 proteins, parvalbumins, and troponin-C.