We fabricate a pair of fiber Bragg gratings (FBGs) by a visible femtosecond laser phase mask scanning technique on passive large-mode-area double-cladding fibers for multi-kilowatt fiber oscillators. The bandwidth of high-reflection (HR) and low-reflection (LR) FBG is ∼1.6nm and 0.3 nm, respectively. The reflection of the HR-FBG is higher than 99%, and that of the LR-FBG is about 10%. A bidirectional pumped all-fiber oscillator is constructed using this pair of FBGs, a record output power of 5027 W located in the signal core is achieved with a slope efficiency of ∼82.1%, and the beam quality factor M² is measured to be ∼1.6 at the maximum power. The FBGs are simply fixed on a water cooling plate without a special package, and the thermal efficiency of the HR-FBG and the LR-FBG is 2.76°C/kW and 1°C/kW, respectively. Our research provides an effective solution for robust high-power all-fiber laser oscillators.

Side pumping combiners are widely used in fiber laser schemes for their high coupling efficiency, low insertion loss, and multi-point pumping capability. However, side pumping combiners perform differently in coupling efficiency when pumping with a laser diode (LD) and a high-brightness 1018 nm Yb-doped fiber laser (YDFL). In this paper, for the first time, to the best of our knowledge, we investigated the different parameters to fabricate the (2+1)×1 combiner with high coupling efficiency when pumping with an LD and a YDFL, respectively. After optimization, the maximum coupled pump power from one single-pump port of the combiner was 1200 W and 2730 W when pumping with a LD and a YDFL, respectively.

硬X射线调制望远镜是我国第一颗X射线天文卫星, 其载荷低能X射线望远镜采用了SCD型探测器CCD236, 主要对能量在0.7~13.0 keV的软X射线光子进行观测。 卫星发射前, 需要对探测器进行详细的性能标定, 其中包括能量响应矩阵的标定。 能量响应矩阵是能谱分析的关键。 CCD236探测器输出能谱并不是观测光源的真实发射谱, 而是发射谱与探测器能量响应矩阵的卷积结果。 一般可以通过直接反卷积的方法还原光源的真实能谱。 解谱过程可以看作是一维成像问题, 利用能量响应矩阵与输出能谱进行反卷积解谱。 常用的反卷积算法为Lucy-Richardson迭代算法, 其利用条件几率的贝氏定理反复进行运算, 进而对输出能谱进行反解, 得到观测光源的真实发射能谱。 通过能量响应矩阵对CCD236探测器的⁵⁵Fe测量能谱进行解谱。 经过解谱, 能谱的能量分辨从144.3 eV提升到了65.6 eV@5.9 keV, 连续谱成分被明显地抑制, 提高了能谱的峰背比。 反解能谱由两个半峰全宽很小的(<70.0 eV)高斯峰组成, 两成分的强度比为8.4, 能够很好地表征真实发射谱的结构。 利用这种方法可对材料X射线荧光谱进行解谱, 还原材料的荧光谱, 提高能谱的能量分辨。 反解结果中主要元素各类荧光线通过解谱彼此独立, 能谱峰背比很高, 可以很好地用于X射线荧光分析中, 提高荧光谱的质量。