Factors influencing optical uniformity of YAG single-crystal fiber grown by micro-pulling-down technology

Abstract

Single-crystal fiber (SCF) combines the advantages of bulk crystal and glass fiber gain media and shows broad application prospects in all-solid-state lasers. In this work, high-quality crack-free Nd:YAG SCFs with diameters of 0.8–1 mm were successfully grown by the micro-pulling-down (μ-PD) method. The as-grown SCFs showed homogeneous Nd³⁺ distribution, with a diameter fluctuation of less than 5%. The X-ray Laue patterns on the different crystal positions also revealed good crystalline consistency. Moreover, the core stress problems were investigated in terms of growth orientation to improve the crystal quality, and seed crystals with orientation of <111>, <100> and <100> to <110> 15° were used for crystal growth. Continuous-wave laser operations at 1064 nm were realized with the as-grown Nd:YAG SCFs. The maximum output of 8.32 W with a laser beam quality factor M² = 1.08 was achieved.