基于拓扑绝缘体的中红外高能量光纤激光器研究

Different from regular insulator or metal, Topological Insulators (TI) are electronic materials that have a bulk band gap like an ordinary insulator but have protected conducting states on their edge or surface. The surface state on the boundary of TI behaves as Dirac relativistic particles like graphene. For the unique structures, rich scientific interests, and widely applications, TIs have become the focus of the international scientific research. Recently, our group found experimentally that the TIs have excellent nonlinear optical properties, such as broadband saturable absorption, high modulation depth and high damage threshold. These characteristics are required by high energy passively mode-locked fiber lasers. Triggered by the requirements of high energy mid-infrared 2 μm fiber lasers, the saturable absorption optical properties at mid-infrared 2 μm of TIs will be studied, and the saturable absorption optical characteristics of TIs will be uncovered experimentally. Based on the saturable absorption characteristics of TI, high energy, stable, self-starting dissipative soliton fiber laser at mid-infrared 2 μm will be demonstrated, and the mechanisms of high energy dissipative solitons in it and the evolution of different dissipative solitons states will be investigated.

拓扑绝缘体不同于传统意义上的绝缘体和金属，其体态是绝缘体，而其表面或者边缘态电子具有和石墨烯类似的狄拉克准粒子行为。因其独特的结构、丰富的科学内涵及广阔的应用前景，拓扑绝缘体已经成为了国际前沿科学研究的焦点。最近，我们实验发现拓扑绝缘体具有优异的非线性光学性质：宽带的可饱和吸收，高的调制深度和高的损伤阈值，而这些特性正是高能量被动锁模激光器中可饱和吸收体所需要的。本项目针对中红外2 μm光纤激光器能量提升的需求，开展硒化铋等拓扑绝缘体材料在中红外2 μm处的可饱和吸收光学特性研究及应用。实验揭示硒化铋等拓扑绝缘体的可饱和吸收光学特性和规律，并利用其独特的可饱和吸收效应实现中红外2 μm掺铥耗散孤子光纤激光器，探究其中高能量耗散孤子的形成机制及各耗散孤子态的形成条件及演化过程，实现高能量、稳定、自启动的中红外2 μm掺铥耗散孤子光纤激光器。

本项目针对中红外2 μm超短超强脉冲光纤激光器能量提升的需求，开展硒化铋等拓扑绝缘体材料的可饱和吸收特性研究，并在理论和实验上研究了耗散孤子激光器脉冲输出特性，最终实现稳定、高能量、自启动的耗散孤子锁模光脉冲输出。研发出滴加干燥-减薄技术以及PMMA双夹层结构来提升可饱和吸收体性能；探索出不同厚度拓扑绝缘体材料的可饱和吸收特性变化规律；分析出拓扑绝缘体表面态及体态在可饱和吸收体特性中所起作用的物理本质；测量出不同分散液对可饱和吸收特性的作用规律；通过理论计算，得出红外2 μm色散管理负色散光纤激光其中增益带宽、双折射、输出耦合比、以及可饱和吸收体的调制深度对输出脉冲参数的作用规律；得出红外2 μm正色散耗散孤子激光器中可饱和吸收体的调制深度和饱和功率以及激光腔中增益带宽和输出耦合率对耗散孤子脉冲的脉冲宽度及脉冲能量的作用规律；优化激光腔参数及拓扑绝缘体可饱和吸收体参数，得到了超短，稳定，高能量的耗散孤子激光器，最大输出脉冲能量为5.3 nJ；此外，还拓展了另外一个可饱和吸收体黑磷，并基于黑磷，得到了稳定的掺铒调Q和锁模脉冲输出；充分利用黑磷的超快弛豫时间，论证可饱和吸收参数以及激光腔参数对脉冲输出特性的影响，得到了全负色散掺铒光纤激光器中最短的脉冲输出。基于项目执行期取得的进展和成果，共发表高水平论文20余篇，申请获得国家级、省部级项目共2项。