多壁碳纳米管光限幅特性的研究

用化学气相沉积法制备了多壁碳纳米管，并将其溶解在甲苯溶液中.用波长为1064nm的皮秒脉冲激光测量该样品的透过率，发现了非常明显的光限幅特性.当入射光强较小时，透射光强度随入射光强度的增大而增大，输出与输入为线性关系；随着入射光强的增大，透射光强增长的速度明显变慢，并逐渐趋于饱和.当入射光强度较小时，样品的透过率接近100%；而当入射光强为8GW/cm²时，非线性透过率达到30%.根据三光子吸收理论计算，理论拟合与实验结果非常符合，说明多壁碳纳米管的三光子吸收产生了光限幅效应.实验测关键词：多壁碳纳米管光限幅三光子吸收

Optical limiting performance of multi-walled carbon nanotubes

The multiwalled carbon nanotubes (MWNTs) were synthesised by chemical vapor deposition and then dissolved in toluene solution. It is discovered experimentally that MWNTs have obvious optical amplitude limiting when the transmittance is measured by means of ps laser pulses with wavelength of 1064nm. In the case of low incident intensity, the transmittance varies linearly with incidenct intensity. However, the transmittance increases slowly under the condition of high incidenct light intensity and at last becomes saturated. Transmission is near 100% for weak incidenct light. But it is 30% when incidence intensity is 8GW/cm². The calculated results based on three-photon-absorption theory agree well with the experimental results and it is inferred that the optical limiting of MWNTs results from its three-photon-absorption. The absorption coefficient γ is 1.36×10^-20cm³/W² and its corresponding absorption section σ′₃ is 2.8×10^-77cm⁶·s².