Fabrication and Characterization of High‐Dimension Single‐Crystal Yb:YAG Ingots Grown by Horizontal Directed Crystallization Method

• Published in: Crystal research and technology (1979) 2020-12, Vol.55 (12), p.n/a
• Main Authors: Kajan, Juraj, Volkov, Mikhail, Damazyan, Grigori, Mukhin, Ivan, Gregor, Tomáš, Palashov, Oleg
• Format: Article
• Language: English
• Subjects: facet growth; high‐dimension single‐crystal growth; horizontal directed crystallization; Yb:YAG crystal quality
• ISSN: 0232-1300; 1521-4079
• DOI: 10.1002/crat.202000105

The research conducted herein builds upon the achievement of a successful and stable 170 × 300 × 35 mm YAG and 5% Yb:YAG single‐crystals production via the horizontal directed crystallization method. Based on the analysis of residual birefringence pattern in analyzed ingots, a hypothesis is proposed—debating that in certain stages of the growth, {211} facets start to form within some sections of the crystallization front. The sensitivity of the {211} facets to temperature fluctuations seems to cause striations in the facets’ growth sectors. In a later stage of the growth process the slope of the crystallization front naturally changes, which seems to reduce the formation of facets considerably. As a result, the rear part of the crystal achieves the best optical quality. The samples extracted from that portion of the ingot, after annealing, possess good optical quality and heat release of 0.004 1/m at 1070 nm, which is quite low, and is considered a good result for the garnet family of crystals. The lasing experiment with thin‐disk geometry shows a slope efficiency of 52% and proves that the material is suitable for high‐power lasers application. Herein, the quality specifics of 170 × 300 × 35 mm YAG and Yb:YAG single‐crystals produced via vacuum horizontal directed crystallization equipment incorporating a graphite thermal unit are analyzed. This work sheds light on the issue of facet formation in the given method, analyzing quality changes throughout the crystal's volume while contemplating the causes for various defects formation.