提出了单层石墨烯包裹双锥形微纳光纤复合波导结构, 构建了730～1 700 nm超宽带微纳光纤波导全光调制器。 通过火焰拉锥法将一根标准的通信单模光纤拉成具有双锥形的微纳光纤, 在保证通光率的前提下可以极大的提升微纳光纤处的倏逝波与物质的相互作用。 利用石墨烯的“超级特征”, 即单原子层厚度、 线性色散的能带结构、 超强的载流子带间跃迁及极短的弛豫时间和超宽带光与物质相互作用等, 将单层石墨烯作为可饱和吸收体, 包裹在双锥形微纳光纤波导的锥体上, 以增强该复合波导表面倏逝波与石墨烯的相互作用。 静态和动态全光调制实验中采用传统808 nm低功率LD作为泵浦光, 对谱宽为480～1 700 nm的超连续谱探测光实现了光光调制, 其泵浦光功率低于50 mW, 调制深度大于5.7 dB, 调制速率达到~4 kHz。 该微纳光纤波导全光调制器, 在保证调制深度的情况下, 用更低的泵浦功率实现了超宽带的全光调制, 以简单、 有效、 廉价的方式兼容了当前高速光纤通信网络, 打开了一扇未来对微纳超快光信号处理的大门。

In this paper, a creative and novel composite waveguide based monolayer graphene-clad microfiber (MGCM) device was designed to achieve ultra-broadband (730～1 700 nm) microfiber waveguide all-optical modulator. We took the biconical microfiber from a standard telecom single mode fiber with flame biconical taper method with low transmission loss, which enhances the evanescent wave and material interaction on the microfiber surface. Using the super-features of graphene, such as atomically thin, linearly dispersive band structure, ultra broadband light-matter interaction, strong interband transitions and ultra-fast carrier relaxation time, monolayer graphene was wrapped as a saturable absorber on the cone of the biconical taper fiber to enhance the interaction between the evanescent wave and monolayer graphene on the surface of the composite waveguide. Both the static and dynamic all-optical modulation experiments were carried out and we achieved supercontinuum (480～1 700 nm) light modulation by chopping the conventional low-power CW laser diode (808 nm) with pump power under 50 mW and the modulation depthsare more than 5.7 dB, the modulation speed is measured to be ~4 kHz. The all-optical modulator based on microfiber composite waveguide achieves ultra-broadband all-optical modulation with lower pump power while ensuring the depth of modulation. It was compatible with the current high-speed optical fiber communication networks in a simple, effective and inexpensive way, which paes the way for to micro/nano ultrafast optical signal processing.