Nanostructured Active Fiber for Mode-Locked and Q-Switched All-Fiber Laser Systems

Mode-locked and Q-switched all-fiber lasers using nanostructured core silica fiber are demonstrated. A novel active fiber has been developed, consisting of a collection of discrete nanorods doped with ytterbium and erbium within an aluminosilicate matrix. The arrangement of nanorods within the fiber core dictates the spatial distribution of amplification and refractive index, enabling the tailored design of the fiber's modal characteristics and dispersion properties. We demonstrate that the employed pumping strategy, which involves stimulating Yb3+ ions situated in nanorods and leveraging a non-radiative energy transfer from Yb3+ to Er3+ ions in distinct nanorods, is effective. This approach facilitates efficient laser performance comparable to fibers with a continuous dispersion of active ions throughout the core. The femtosecond mode-locked pulse at wavelength of 1560 nm, featuring a bandwidth of 5.2 nm, a pulse duration of 860 femtoseconds, and an RF spectral purity with an extinction ratio of 80 dB has been successfully obtained. These results underscore the potential of the nanostructured core fiber concept as an active medium in ultrafast, all-fiber devices.本研究展示了基于纳米结构纤芯石英光纤（nanostructured core silica fiber）的锁模（mode-locked）与调Q（Q-switched）全光纤激光器。研究开发了一种新型有源光纤（active fiber），其结构为在铝硅酸盐基质（aluminosilicate matrix）中嵌入多根掺杂镱（ytterbium）与铒（erbium）的离散纳米棒。光纤纤芯内纳米棒的排布决定了增益与折射率的空间分布，可实现光纤模式特性与色散特性的定制化设计。本研究证实所采用的泵浦策略切实有效：该策略通过激发纳米棒内的Yb³+离子，并利用不同纳米棒中Yb³+与Er³+离子间的非辐射能量转移（non-radiative energy transfer）实现泵浦。该方案可实现与纤芯内有源离子连续分布的光纤相当的高效激光输出性能。本研究成功获得了波长为1560 nm的飞秒（femtosecond）锁模脉冲，该脉冲带宽达5.2 nm，脉冲宽度为860飞秒，其射频（RF）光谱纯度的消光比（extinction ratio）高达80 dB。上述研究结果凸显了纳米结构纤芯光纤概念作为有源介质，在超快全光纤器件中的应用潜力。