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

• Published in: Optical materials Vol. 141; p. 113980
• Main Authors: Nizhankovskyi, S.V., Vovk, O.O., Kozlovskyi, A.A., Sidelnikova, N.S., Siryk, YuV, Kovalenko, N.O., Vorona, I.O., Sofronov, D.S., Skoryk, S.M., Baumer, V.N., Bryleva, K. Yu, Pritula, I.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2023
• Subjects: Co-doped spinel crystal; Magnesium-aluminum spinel; Molybdenum crucible; Optical absorption; Passive Q-switches; Co-doped spinel crystal; Passive Q-switches; Magnesium-aluminum spinel; Optical absorption; Molybdenum crucible
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2023.113980

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.
•Single crystals of Co-doped magnesium-aluminum spinel were grown using the Mo crucible.•Growing crystals in molybdenum crucibles are more attractive than in iridium crucibles.•Optical absorption spectra of the Co-doped spinel crystal were studied.•Co2+ ions replace Mg2+ ions in the tetragonal positions of the spinel structure.•Tests of Q-switches based on Co-doped spinel crystals showed the pulsed generation.