Spectroscopic properties of Ho3+ optical centers in CaF2 crystals at the two-micron laser transition

Abstract

The spectroscopic properties and lifetimes of various Ho3+ optical centers at the two-micron 5I7→5I8 laser transition were studied in CaF2 crystals at cryogenic temperatures (15 K, 77 K) using resonant selective excitation of holmium ions. For the first time, the excitation and luminescence spectra of three different optical centers with 5I7 level lifetimes of ~11 ms, ~18 ms, and ~26 ms were identified. The 18 ms lifetime optical center was ascribed to tetragonal one, the center with 26 ms lifetime is most likely a cubic one, and the center with a lifetime of 11 ms is a clustered optical center.