Optical and laser characteristics of Сo-doped magnesium-aluminum spinel crystals grown using molybdenum crucible

Abstract

Single crystals of Co-doped magnesium-aluminum spinel (MALO:Co) are used for Q-switching of laser radiation at λ = 1.54 μm. Usually, they are grown by the Czochralski method from iridium crucibles that are too expensive. This investigation demonstrates the possibility of obtaining MALO:Co single crystals by the horizontal directional crystallization method using a molybdenum crucible in Ar + (CO, H2) protective reducing medium.The obtained MALO:Co crystals have the spinel structure of MgO‧xAl2O3 with 1 ≤ x < 1.15, and the impurity of molybdenum in them does not exceed 0.019 wt%. Co2+ ions replace Mg2+ ions in the [MgO4] tetrahedral environment. This is confirmed by the broad absorption bands (λmax ≈ 600 nm and λmax ≈ 1400 nm) in Vis-IR spectra. The absorption bands in the UV region of the spectrum are shown to originate from the complexes of point defects that can be eliminated by subsequent annealing in oxidizing/reducing environment. Experimentally shown is the possibility to obtain monoimpulses with the energy of ∼ 1–2 mJ and ∼10–15 ns duration at a wavelength of ∼1.54 μm in passive Q-switches based on MALO:Co crystals.