ABSTRACT
The bulk laser-induced damage threshold (LIDT) fluence of Ti:sapphire is determined under single-pulse irradiation from the femtosecond to nanosecond temporal regimes in the visible and near-infrared spectral domains. In the range of explored laser conditions, the LIDT fluence increases with both pulse duration and wavelength. The results are also compared to laser interaction with sapphire samples and show an increased resistance to laser damage when the material is doped with Ti(3+) ions. These conclusions are of interest for robust operation of high-peak-power femtosecond Ti:sapphire laser chains.
ABSTRACT
Candidate pre-main-sequence stars were observed in the bar of the Large Magellanic Cloud during the search for dark matter in the galactic halo. Seven blue stars of apparent visual magnitude 15 to 17 had irregular photometric variations and hydrogen emission lines in their optical spectra, which suggested that these stars are pre-main-sequence stars of about 10 solar masses. These stars are slightly more massive and definitely more luminous than are Herbig AeBe pre-main-sequence stars in our own galaxy. Continued observations of these very young stars from another galaxy, which are probably at the pre-hydrogen-burning stage, should provide important clues about early stages of star formation.