Repetition rate continuously tunable 10-GHz picosecond mode-locked fiber ring laser

A couple of simple-structure phase modulators were used in active mode-locked fiber laser to implement repetition rate continuous tuning. The laser produces pulse as short as 5.7 ps whose repetition rate tuning can cover the spacing of the adjoining order mode-locking frequencies.     

钠离子电池工作原理及关键电极材料研究进展

由于钠资源价格低廉、分布广泛等优点,钠离子电池及其关键电极材料的研究近年来引起了广泛的关注.然而,与锂相比,钠的离子半径大得多,使其在储钠材料中的迁移速度过慢而严重地限制了钠离子电池倍率性能的提升和储钠容量的表达,而且钠元素具有更高的相对原子质量,也在理论上限制了钠离子电池的能量密度.因此,开发先进的、利于钠离子脱嵌的电极材料是开发高性能钠离子电池的关键.本文在钠离子电池工作原理的基础上,着重介绍了几类典型的关键电极材料,并对它们的研究进展进行了简要综述.