Alon Yair, Halstuch Aviran, Sidharthan Raghuraman, Yoo Seongwoo, Ishaaya Amiel A
Opt Lett. 2020 Aug 15;45(16):4563-4566. doi: 10.1364/OL.397415.
We demonstrate a direct inscription of a fiber Bragg grating (FBG) in the active cores of an Yb-doped large mode area multicore fiber (MCF). An ultrashort pulsed laser is used to inscribe the FBG simultaneously in all six cores. In order to validate the FBG reflection and uniformity, the FBG is incorporated as a rear mirror in a fiber laser oscillator setup. The MCF, which has been fabricated in-house, has six cores located in a hexagonal-ring shape, each with a 19 µm diameter and an NA of ∼0.067. A reflection of ∼96 was measured at a center Bragg wavelength of ∼1062 for the inscribed FBG. The laser performance of the MCF with the femtosecond inscribed FBG at its end shows a similar performance to lasing with a free-space commercial volume Bragg grating as the rear-reflector. A slope efficiency of ∼72.4 and a maximum (pump limited) output power of 51.8 W have been obtained for the FBG setup. An effective of 3.88, indicating a somewhat multimode operation and a narrow bandwidth of ∼0.19, has been measured for this fiber laser.
我们展示了在掺镱大模场面积多芯光纤（MCF）的有源纤芯中直接写入光纤布拉格光栅（FBG）。使用超短脉冲激光在所有六个纤芯中同时写入FBG。为了验证FBG的反射和均匀性，将FBG作为后向反射镜并入光纤激光振荡器装置中。我们自制的MCF有六个呈六边形排列的纤芯，每个纤芯直径为19 µm，数值孔径约为0.067。对于写入的FBG，在中心布拉格波长约为1062处测得的反射率约为96%。在其末端带有飞秒写入FBG的MCF的激光性能与以自由空间商用体布拉格光栅作为后向反射器的激光性能相似。对于FBG装置，已获得约72.4%的斜率效率和51.8 W的最大（泵浦限制）输出功率。已测得该光纤激光器的有效模式数为3.88，表明其存在一定程度的多模运转，带宽约为0.19。
