为了研究石墨烯器件在中红外波段的光限幅机理, 采用化学气相沉积法制备出层数可控的石墨烯薄膜CaF2镜片, 并基于MgO∶PPLN周期极化晶体搭建了全固态中红外光学参量振荡器, 利用3 μm~5 μm波长可调谐的闲频光开展了石墨烯薄膜散射实验, 测量了石墨烯薄膜的散射信号与入射光强度变化的归一化曲线。当闲频光能量超过1 J/cm2时, 石墨烯被迅速汽化, 电离形成的微小等离子体和石墨烯微片对入射闲频光产生多重非线性散射, 散射能量信号呈现出快速非线性增长趋势, 并且散射能量信号值的增长率与闲频光的入射波长成反比, 与石墨烯的层数成正比关系, 从而验证了石墨烯对中红外波段激光较强的非线性散射使其具有光限幅效应。

The layer controlled graphene film CaF2 mirrors were prepared by chemical vapor deposition method to study optical limiting mechanism of the graphene devices in 3 μm~5 μm infrared band, and an all-solid-state infrared optical parametric oscillator was builted based on a periodic polarization crystal MgO∶PPLN. The experiment about scattering of graphene films in the integrating sphere was carried out by using the idler light in 3 μm ~5 μm wave band. The normalized curve of scattering signal of graphene films and changes of the incident light were measured. It was found that when the idle light energy was more than 1 J/cm2, and the scattering energy signal with the incident light intensity exhibited a fast nonlinear growth trend. In addition, the growth rate of the scattering energy signal was inversely proportional to the incident wavelength of the idle frequency light, which was proportional to the number of layers of graphene. Results show that the optical limiting mechanism of graphene films in 3 μm~5 μm in the infrared band might be due to the rapidly-vaporized graphene, the formation of micro plasma ionization and the nonlinear scattering.