基于大尺寸少层MoTe2/WTe2锁模掺铥高功率光纤激光器研究

Fiber laser at 2um has important applications in medical and scientific fields. The semiconductor saturable absorber mirror (SESAM) was mostly used as the passive modulation element in 2μm pulsed laser in early time. However, commercial SESAM is costly and production process is complicated. Especially, the saturable absorption bandwidth of SESAM is narrow. Researchers began to develop new mode-locked devices to make up for the disadvantages of SESAM. Pulsed fiber lasers at 2um based on 2-D materials were reported in recent years. This trend represented that 2-D materials have important applications in realizing pulse fiber laser at 2um with high power and ultrashort pulse. MoTe2/WTe2 have similar energy level structure compared with traditional MoS2/WS2. Furthermore, MoTe2/WTe2 have smaller band gap (less than 1 eV) and higher electric conductivity compared with MoS2/WS2. These properties represent that MoTe2/WTe2 are especially suitable for mid-infrared waveband. However, there are no related researches that MoTe2/WTe2 were used as saturated absorber of Tm-doped fiber laser. In this research, we plan that MoTe2/WTe2 are used as saturated absorber of Tm-doped fiber laser to realize stable mode-locked laser with high power at 2um.

2μm光纤激光器在医疗与科研等方面具有重要的应用。前期2μm脉冲激光器多采用半导体可饱和吸收镜（SESAM）作为被动调制元件。然而，商用的SESAM具有价格昂贵、制作工艺复杂，尤其是可饱和吸收带宽窄。科研工作者们开始寻找全新的技术研发此类锁模元件，以弥补SESAM所存在的不足。近年来国内外相继报道了基于2D材料实现2μm脉冲光纤激光器。这种趋势说明了2D材料在实现高功率2μm超短脉冲激光器方面具有重要的应用。其中与传统的过渡金属硫化物MoS2/WS2相比，MoTe2/WTe2与MoS2/WS2具有相似的能级结构，并且MoTe2/WTe2具有更小的带隙(小于1 eV)以及更高的导电率，特别适合应用在中红外波段。目前尚无相关研究将MoTe2/WTe2应用在2μm波段。在本研究中，我们拟使用MoTe2/WTe2作为掺铥光纤激光器的可饱和吸收体，以在2μm波段得到稳定的高功率锁模激光输出。

2μm波段的高能量超快激光在科研、医疗以及军事等领域具有重要的应用。可饱和吸收体是实现超快激光输出的核心元件。近年来多种低维材料被用作可饱和吸收体应用到光纤激光器中以获得高能量超快激光输出。然而，由于受到损伤阈值以及调制深度等因素的限制，采用常规的可饱和吸收体在2μm波段实现高能量超快激光输出仍是一件非常富有挑战性的事情。为了在2μm波段实现高能量超快激光输出，本研究围绕“基于大尺寸少层MoTe2/WTe2锁模掺铥高功率光纤激光器研究”，采用磁控溅射法与化学气相沉积法研制了一类基于微纳光纤的新型可饱和吸收体，大幅提高了其损伤阈值与调制深度，并基于此类可饱和吸收体在2μm波段成功实现了高能量超快激光输。对于利用磁控溅射法制备的基于微纳光纤的MoTe2与WTe2可饱和吸收体，我们分别在2μm波段成功实现了功率与脉宽为212mW/1.3ps与39.9mW/1.25ps激光输出。此外，我们还利用磁控溅射法制备的基于微纳光纤的MoTe2可饱和吸收体在1.5μm波段成功实现了功率与脉宽分别为57mW与229fs的激光输出。对于利用化学气相沉积法制备的基于微纳光纤的MoTe2可饱和吸收体，我们在2μm波段成功实现了功率与脉宽分别为36.7mW与952fs激光输出。我们的研究结果表明MoTe2与WTe2可作为2μm波段的优异的可饱和吸收体材料，并且利用磁控溅射法与化学气相沉积法可制备出具有高损伤阈值与大调制深度的高性能可饱和吸收体，有利于高能量超快激光的产生。