Growth of 60 mm-diameter Yb:CNGG single crystals with disordered coordination structure for high-energy laser systems

Abstract

High-energy solid-state pulsed lasers are used for intriguing applications in various fields and typically require amplification gain media with large dimensions, low pump saturation density, moderate emission saturation flux, and superior energy storage properties. Yb-doped calcium niobium gallium garnet (Yb:CNGG) crystals are promising gain candidates for laser amplification. However, obtaining large-sized crystals is still a challenge due to the deviation of chemical compositions and accompanying chemical stress arising from the intrinsic disordered coordination structure of the crystal. Herein, we report the growth of Yb:CNGG crystals to large sizes by thoroughly managing the influences of raw materials and temperature field. By optimizing the initial chemical composition and temperature gradient distribution, we successfully grew a 60 mm-diameter Yb:CNGG crystal without any cracks. The subsequent results indicated that the as-grown crystal exhibited satisfactory crystallinity (full width of half maximum of 38.02′′), moderate thermal conductivity (3.98 W m⁻¹ K⁻¹), excellent optical uniformity (3.85 × 10⁻⁴), a low fluctuation of the Yb doping concentration (±3.57%), and a large laser damage threshold (51.03 J cm⁻²). Our findings not only provide a promising gain medium for developing high-energy laser amplification systems but also are significant for growing large-sized crystals with disordered coordination structures.