Two side-pumping schemes suitable for the development of an ultraviolet femtosecond amplifier system using a Ce<sup>3+</sup>:LiCaAlF<sub>6</sub> crystal are reported. Firstly, a Bethune-type prismatic cell configuration that uniformly illuminates the four sides of a micro-pulling down method-grown crystal is used to amplify 290 nm, femtosecond pulses with no significant increase in pulse duration and B-integral. The second pumping scheme uses a two-side-pumped large crystal. These two side-pumping schemes can pave new possibilities for achieving high-energy ultraviolet femtosecond pulses.
Yb:doped Lu<sub>2</sub>SiO<sub>5</sub> (Lutetium orthosilicate, LSO) is an optically biaxial crystal with laser emission in the range 1000- 1100 nm. It features different absorption and emission spectra for polarization along its three dielectric axes. In this work we have characterized the laser emission properties of Yb:LSO along all the three dielectric axis, evidencing differences that can be exploited in the design of ultrafast laser sources. The material was tested in a longitudinally pumped laser cavity. The laser emission efficiency was found similar along all the three dielectric axes, with slope efficiencies around 90% in most cases. Regarding the tuning range, for the most favourable polarization direction we obtained a continuously tunable emission between 993 and 1088 nm (i. e. 95 nm) peaked at 1040 nm. The tuning curves along the three dielectric axes spanned similar ranges but with relevant differences in the shape.
Transmittance and radiation induced absorbance in VUV-UV-visible spectral region were measured in several binary
and complex fluoride single crystals at room temperature. Influence of the intentional doping and material stochiometry
is demonstrated. X-ray induced coloration and degradation of transmittance characteristics are observed and discussed in
terms of creation of various electron (F-like) and hole (VK- and H-like) centers and in terms of near band-edge transitions
arising due to imperfect periodicity of the lattice in a general sense. It is shown that VUV characteristics cannot be
derived or predicted from those observed in UV-visible spectral region.
High quality fluoride and oxide single crystals for optical, piezoelectric and other applications have been grown by advanced crystal growth techniques. Corquitiite- and Perovskite-type fluoride single crystals - LiCaAlF<SUB>6</SUB>, LiSrAlF<SUB>6</SUB>, KmgF<SUB>3</SUB> and BaLiF<SUB>3</SUB> - have been grown for solid state UV laser applications, and as window materials for next generation optical lithography. La<SUB>3</SUB>Nb<SUB>0.5</SUB>Ga<SUB>5.5</SUB>O<SUB>14</SUB> and La<SUB>3</SUB>Ta<SUB>0.5</SUB>Ga<SUB>5.5</SUB>O<SUB>14</SUB> piezoelectric single crystal of size and quality comparable to La<SUB>3</SUB>Ga<SUB>5</SUB>SiO<SUB>14</SUB>, have been produced. The piezoelectric and deice properties of the crystal were investigated. A search for new langasite-type materials was also performed. Promising new structural materials. Undoped and doped eutectic fibers, have been grown by the micro- pulling-down technique. Undoped and doped(beta) -Ga<SUB>2</SUB>O<SUB>3</SUB> single crystals have been grown by the floating zone technique as promising transparent conductive oxides.
TAG fibers were grown by the micro pulling down method from stoichiometric and alumina rich melts. Using the Czochralski technique polycrystalline TAG samples were obtained from alumina rich melts. It was shown that both growth methods the crystallization of TAP can be avoided by starting from a melt concerning less than 32 mol-% Tb<SUB>2</SUB>O<SUB>3</SUB>.