石墨烯在中红外波段的光限幅效应研究

Study on optical limiting effect of graphene in mid-infrared band

利用纳秒级脉冲量激光的Z扫描方法对不同层数石墨烯薄膜在3μm^5μm中红外波段的光限幅效应开展了研究,获得的开孔Z扫描曲线均呈现出单一谷结构,而闭孔Z扫描曲线没有明显的峰谷对称结构。通过对开孔Z扫描实验数据进行数值模拟,分别得到3层石墨烯在3.010μm、3.522μm、4.326μm和4.880 4μm 4个中心波长处的三阶非线性吸收系数和光限幅阈值分别为11.39×10^(-7)cm/W、10.61×10^(-7)cm/W、9.75×10^(-7)cm/W、8.81×10^(-7)cm/W和3.49J/cm^2、3.75J/cm^2、4.11J/cm^2、4.55J/cm^2;3层、5层和7层石墨烯在3.522μm中心波长处的三阶非线性吸收系数和光限幅阈值分别为10.61×10^(-7) cm/W、11.32×10^(-7) cm/W、11.95×10^(-7) cm/W和3.75J/cm^2、3.41J/cm^2、3.32J/cm^2。实验数据表明,石墨烯在中红外波段产生了较强的非线性反饱和吸收而具有明显的光限幅效应。

The optical limiting effect of the graphene films in mid-infrared band （3 μm-5 μm） was studied using nanosecond pulsed laser Z-scan method. The Z-scan curve obtained from the open aperture experiment showed a single valley structure, but the same structure did not show in the closed-aperture Z-scan curve. Through the fitting and calculation of the open-aper- ture Z-scan curve, the 3-order nonlinear absorption coefficients and the optical limiting thresholds of 3 layers graphene were 11.39 ×10^10-7 cm/W, 10.61×10^-7 cm/W, 9.75×10^-7 cm/W, 8.81×10^-7 cm/W and 3.49 J/cm^2 , 3.75 J/cm^2 , 4.11 J/cm^2, 4.55 J/cm^2 at 3. 010 μm, 3. 522 μm, 4. 326μm and 4. 880 4μm, respectively. The 3-order nonlinear absorption coefficients and the optical limiting thresholds of 3 layers, 5 layers and 7 layers graphene in 3. 522 μm center wavelength were 10.61 ×10^-7 cm/W, 11.32 ×10^-7 cm/W, 11.95 ×10^-7 cm/W and 3.75 J/cm^2 , 3.41 J/cm^2 , 3.32 J/cm^2, respectively. The experimental results show the optical limiting effect of graphene is obvious in the mid-infrared band based on nonlinear reverse saturable absorptlon.