1.3kW Single-mode All-fiber MOPA Based on Low-NA Trench-assisted Ytterbium-doped Fiber

A newly designed and fabricated trench-assisted low-NA (~0.04) fiber was reported. An output power up to 1.3kW with M
²
<; 1.1 was achieved in an all-fiber MOPA based on the fabricated low-NA fiber.