Diode-pumped laser action in a new broadly tunable crystal: Yb/sup 3+/:Sr/sub 3/Y(BO/sub 3/)/sub 3/

Abstract

Summary form only given. The first demonstration of laser action under diode-pumping is herein reported with a Yb:Sr/sub 3/Y (BO/sub 3/)/sub 3/ (Yb:SrYBO or Yb:BOYS) double-borate crystal: 0.9 W were obtained for 2.45 W of absorbed pump power. This new material exhibits a particularly broad emission spectrum (60 nm FWHM) and an unusually broad zero-phonon absorption linewidth (6 nm). The similarity with glasses is striking, although Yb:SrYBO has higher cross sections and presumably better thermal conductivity due to its crystalline structure. These features make this material potentially very attractive for tunable lasers around 1 /spl mu/m and directly diode-pumped femtosecond sources. One major interest is the broad absorption bandwidth at 975 nm, approximately 6 nm, which makes spectral linewidth specifications of high power diodes less demanding. The broad absorption and emission bands are supposed to be linked to vibronic transitions, Yb/sup 3+/-Yb/sup 3+/ pairs effects and multisite behavior. Moreover, a strong crystal field is experienced by the Yb/sup 3+/ ions within the lattice (the /sup 2/F/sub 7/2/ splitting of Yb/sup 3+/ is approximately 800 cm/sup -1/): this should lead to a very small lower laser level thermal population, and reduced reabsorption losses. Last but not least, it is a congruent melting crystal, whose growth was thus carried out by the Czochralski process, leading to high optical quality pieces.