Four-wave-mixing generated by femto-second laser pumping based on graphene coated microfiber structure

Abstract

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 transmission 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.#br#The simulation and experimental results demonstrate that this P-doped graphene coated microfiber hybrid structure 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.