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DOE OSTI2020

Materials Data on LiCaAlF6 by Materials Project

LiCaAlF6 is beta Vanadium nitride-derived structured and crystallizes in the trigonal P-31c space group. The structure is three-dimensional. Li1+ is bonded to six equivalent F1- atoms to form LiF6 octahedra that share corners with six equivalent CaF6 octahedra and edges with three equivalent AlF6 octahedra. The corner-sharing octahedral tilt angles are 57°. All Li–F bond lengths are 2.04 Å. Ca2+ is bonded to six equivalent F1- atoms to form CaF6 octahedra that share corners with six equivalent LiF6 octahedra and corners with six equivalent AlF6 octahedra. The corner-sharing octahedra tilt angles range from 46–57°. All Ca–F bond lengths are 2.31 Å. Al3+ is bonded to six equivalent F1- atoms to form AlF6 octahedra that share corners with six equivalent CaF6 octahedra and edges with three equivalent LiF6 octahedra. The corner-sharing octahedral tilt angles are 46°. All Al–F bond lengths are 1.83 Å. F1- is bonded in a distorted trigonal planar geometry to one Li1+, one Ca2+, and one Al3+ atom.

36 MATERIALS SCIENCE↗

NASA NTRS1995

Spectroscopic Investigation of Ce(3+) Doped Fluoride Crystals

Doping of the trivalent rare-earth cerium ion into fluoride crystals is of interest in producing turnable ultra-violet solid state lasers. These lasers are desirable for many applications in medicine, industry, and scientific research, including remote sensing. High absorption and stimulated emission cross sections of the dipole allowed 4f-5d transitions show promise in cerium as a laser ion in crystals. Several research groups have already reported the observation of stimulated emission of cerium in LiYF4, LiSrAlF6, and LiCaAlF6. However, the color center formation in the crystals due to the excited state absorption of ultra-violet pump light adds difficulty to achieving laser action. We have investigated the spectroscopic properties of cerium such as absorption and emission spectra, and lifetimes in four different fluoride crystals, including LiCaAlF6, LiSrAlF6, KyF4 and LiYF4. We have derived the polarized absorption and stimulated emission cross sections from transmission and fluorescence emission measurements for each of the host crystals. we have measured the lifetime of the lowest 5d level; moreover, investigated the temperature dependence of this lifetime and color center formation. Our results on absorption and stimulated emission cross sections for LiCaAlF6 and LiSrAlF6 are similar to the results already published.

Reinhart, Donald H.↗

NASA NTRS2012

A Solid State Ultraviolet Lasers Based on Cerium-Doped LiCaAIF(sub 6) Crystal Resonator

We report the first demonstration of a UV laser using a high-Q whispering gallery mode (WGM) resonator of Ce+: LiCaAlF6. We show that WGM resonators from LiCaAlF6 can achieve a Q of 2.6 x 10(sup 7) at UV. We demonstrated a UV laser at 290 nm with a pulsed pump laser at 266 nm. The experiments showed the low pump threshold intensity of 7.5 x 10(sup 9) W/m(sup 2) and slope efficiency of 25%. We have also observed lasing delay dynamics. These results are consistent with our modeling and theoretical estimates, and pave the way for a low threshold cw UV laser using WGM resonator cavity.

Whispering Gallery Mode Resonators↗