Passively mode-locked Yb:CNGG laser
Recently we achieved continuous-wave (cw) and Q-switched laser operation of Yb<sup>3+</sup> in the disordered crystal Ca<inf>3</inf>(NbGa)<inf>2−x</inf>Ga<inf>3</inf>O<inf>12</inf> or shortly CNGG [1] previously studied only with Nd-doping [2] and Tm-doping [3]. It is an isotropic material similar to YAG and exhibits a rather high thermal conductivity of 4.7 Wm<sup>−1</sup>K<sup>−1</sup>, about one third of that of YAG which is much larger than for glasses. The disordered nature of the CNGG crystal provides several different lattice positions for the trivalent dopant ions, resulting in significant inhomogeneous broadening in the absorption and emission spectra. The maximum absorption cross section was measured to 3.3·10<sup>−20</sup> cm<sup>2</sup> at 973.5 nm. Apart from the zero-phonon line the maximum emission cross section is 2.5·10<sup>−20</sup> cm<sup>2</sup> at 1028 nm with a bandwidth of 21 nm (FWHM), roughly twice that of Yb:YAG. The measured fluorescence lifetime amounts to 791 µs. We demonstrated 2.0 W of cw output power with a slope efficiency of 40% for Yb:CNGG and the passively Q-switched operation delivered 1.35 W of average output power at a PRF of 16.7 kHz [1]. Here we demonstrate passive mode-locking of the disordered laser crystal Yb:CNGG using a semiconductor saturable absorber mirror (SESAM).
Kerr-Lens Mode-Locked Diode-Pumped Yb:YAG Laser with the Transverse Mode Passively Stabilized
We have developed a Kerr-lens mode-locked diode-pumped Yb:YAG laser in which the transverse mode is passively stabilized. The mode-locking scheme can be used for various diode-pumped Yb-doped bulk lasers. The pulse duration is as short as 100 fs, which is to our knowledge the shortest pulse ever produced from an Yb:YAG laser. The center wavelength and laser output power are 1051 nm and 151 mW, respectively.
Global attractivity in time-delayed predator-prey systems
Abstract For a predator-prey model with time-delay due to gestation, criteria are obtained for persistence and global attractivity. The global attractivity criteria apply only to models with a decreasing prey isocline.