基于飞秒激光抽运的石墨烯包裹微光纤波导结构的级联四波混频研究

摘要

基于石墨烯的光学非线性特性和器件研究正在成为新一代微纳光子器件的一个重要方向. 采用峰值功率为kW量级的飞秒脉冲抽运和P型掺杂石墨烯薄膜包裹的微光纤所构成的复合波导结构,在1550 nm波段成功激发并观察到级联四波混频现象. 实验结果表明, 这种P型掺杂石墨烯包裹的微光纤复合波导具有非线性系数高、结构紧凑,可承受高功率和超快响应的特点,对基于该结构的级联四波混频特性的研究在基于超快光学的多波长光源、光参量放大以及全光再生等领域具有参考价值和应用意义.%Nonlinear optics researches of graphene-based four waves mixing (FWM) effect are important for a new generation of photonic devices. Compared with the ordinary graphene materials, the P-doped graphene based hybrid waveguide structure is more conducive to the simulating of the third-order nonlinear effect in low power due to its smaller transmis-sion loss. In this work, we propose a P-doped graphene coated microfiber hybrid waveguide structure for femto-second laser pumping excited FWM. By the simulations, we analyze the HE11 mode distribution and the effective refractive index of the silica microfiber and P-doped graphene coated microfiber hybrid waveguide with different fiber diameters at a wavelength of ～1550 nm. We also implement the fabrication processing and characterize this P-doped graphene coated microfiber hybrid waveguide. In the experiments, we utilize a femto-second laser as the pump laser with a peak power up to kW. As the graphene material and the microfiber contribute to the nonlinearity, the cascade FWM could be obtained. Experimental results demonstrate that when the peak power of the injection pump is fixed at 1.03 kW, by adjusting the detuning in wavelength to the length less than 10.0nm, there are four sets of frequency components that can be observed. In the present paper, we provide the relationship among the detuning in wavelength, the pump power and the the power of Stokes peak. These results indicate that under the condition of a few nanometer detuning wavelength, when the pump power is fixed at 14.1 dBm and the detuning wavelength is 6.7 nm, there are second order Stokes light and the second order anti-Stokes light, which can be observed, here the obtained conversion efficiency is up to-60 dB, which can be improved by optimizing the waveguide structure and increasing the pump power. Meanwhile, this FWM processing is also fast due to the fast pumping laser. The simulation and experimental results demonstrate that this P-doped graphene coated microfiber hybrid struc-ture has the advantages of highly nonlinearity, compact size and withstanding high power ultrafast laser, showing the important research value and potential applications in fields based on ultrafast optics, such as multi-wavelength laser, phase-sensitive amplification, comb filters and all-optical regeneration.