YTTERBIUM-DOPED APATITE-STRUCTURE CRYSTALS - A NEW CLASS OF LASER MATERIALS

A new class of Yb-lasers is summarized in this article. The apatite fa mily of crystals, based on the hexagonal structure of the mineral fluo rapatite, has been found to impose favorable spectroscopic and laser p roperties on the Yb3+ activator ion. Crystals of Yb-doped Ca5(PO4)3F, Sr5(PO4)3F, CaxSr5-x(PO4)3F, and Sr5(VO4)3F have been grown and invest igated. Several useful laser crystals have been identified which offer a variety of fundamental laser parameters for designing diode-pumped systems. In general, this class of materials is characterized by high emission cross sections (3.6-13.1 X 10(-20) cm2), useful emission life times (0.59-1.26 ms), a strong pump band (sigma(abs)=2.0-10.0 X 10(-20 ) cm2), and pump and extraction wavelengths near 900 and 1045 nm, resp ectively. Efficient lasing has been demonstrated for several of the me mbers of this class of materials, and high optical quality crystals ha ve been grown by the Czochralski method. A summary of the laser parame ters and a discussion of the Yb:apatite class of lasers is presented.