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Grain growth and significant Fe diffusion in polycrystalline ZnS at elevated temperatures and pressures
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Paper Abstract

Middle-infrared (mid-IR) lasers enabling a wide range of scientific, medical, technological, and defense related applications continue to enjoy a strong demand. Transition metal (TM) doped II-VI chalcogenides are appealing mid-IR gain medial providing direct access to 1.8-6 μm spectral range. . II-VI chalcogenides are available in single crystal and in polycrystalline forms. With respect to single crystals, polycrystalline gain elements fabricated by postgrowth thermal diffusion of TM impurities in II-VI hosts feature better optical quality and enable superior laser characteristics. Despite significant progress in post-growth thermal diffusion technology, there are still some difficulties associated with the diffusion of certain TM ions in certain II-VI hosts. Specifically, the diffusion length Fe in ZnS during ~1 month annealing at 950°C is of the order of 0.1 mm. In this work, enhancement of diffusion coefficient under Hot Isostatic Pressing, at temperature and pressure of 1350°C and 2000 atm, and effect of these extreme conditions on the overall optical quality of the crystal were studied. The high temperature was applied to increase the diffusion rate, and the high pressure was needed to suppress strong sublimation and sphalerite - wurtzite phase transition at elevated temperatures. Under these conditions, the diffusion coefficient Fe in ZnS was enhanced by 5500 times as compared to standard diffusion processes carried out at 950°C. It was also demonstrated that the grain size had grown from ~30μm to ~5.5mm, which is believed to be another reason for efficient diffusion besides the elevation of temperature. The XRD patterns were measured such that the X-ray beam falls on a single grain. The XRD patterns showed only peaks characteristic to single crystals with zinc blende structure. Lasing characterization was performed to investigate the optical quality of the crystal. Slope efficiencies of 23.2% and 15.4% were obtained for TM11 and TM00 modes of operation, respectively. The emission of the laser was demonstrated to be in the 3840-3920 nm.

Paper Details

Date Published: 15 February 2018
PDF: 6 pages
Proc. SPIE 10511, Solid State Lasers XXVII: Technology and Devices, 105111R (15 February 2018); doi: 10.1117/12.2290957
Show Author Affiliations
Ozarfar Gafarov, The Univ. of Alabama at Birmingham (United States)
Dmitriy Martyshkin, The Univ. of Alabama at Birmingham (United States)
Vladimir Fedorov, The Univ. of Alabama at Birmingham (United States)
Sergey Mirov, The Univ. of Alabama at Birmingham (United States)

Published in SPIE Proceedings Vol. 10511:
Solid State Lasers XXVII: Technology and Devices
W. Andrew Clarkson; Ramesh K. Shori, Editor(s)

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