Muller Olivier, Lutz Yves, Teissier Anne, Moeglin Jean-Pierre, Keller Valérie
Institut Franco-Allemand de Recherches de Saint-Louis, 5 rue du Général Cassagnou F-68301 Saint-Louis, France.
Appl Opt. 2010 Mar 1;49(7):1097-103. doi: 10.1364/AO.49.001097.
The optical limiting behavior of multiwalled carbon nanotube (MWCNT) powder in chloroform solution under CO(2) infrared laser irradiations is reported for, to our knowledge, the first time. Here we demonstrate the pure thermal origin of the optical limiting effect in the 160 ns time scale studied. The Z-scan technique appears to be an excellent tool for experimental evaluation of the nonlinear refractive index. An experimental model for the optical limiting behavior of MWCNT suspensions in chloroform is presented. The occurrence of a laser-induced thermal lens through the absorption of energy by the MWCNTs and subsequent heat transfer to the solvent, followed by solvent vapor bubble growth, is the main factor governing the observed drop in transmittance. Pump-probe experiments have been performed to obtain some quantitative estimation of both the rise and decay times of the thermal lensing phenomenon. It was found that the early probe signal decay, tau(1)=149 ns, was of the same order of magnitude as the rise time of the thermal lens, tau(r)=121 ns. When the nonlinear scattering was considered, a total decay time of tau=1.8 micros was obtained. A recovery time for the thermal lens of several tens of milliseconds has been experimentally determined, which is in good accordance with the theoretical value.
据我们所知，首次报道了多壁碳纳米管（MWCNT）粉末在氯仿溶液中于CO₂红外激光辐照下的光限幅行为。在此我们证明了在研究的160 ns时间尺度内光限幅效应的纯粹热起源。Z扫描技术似乎是用于实验评估非线性折射率的出色工具。提出了MWCNT在氯仿中悬浮液光限幅行为的实验模型。通过MWCNT吸收能量并随后将热量传递给溶剂，接着溶剂汽泡生长而产生激光诱导热透镜，这是导致观察到的透射率下降的主要因素。已进行泵浦 - 探测实验以对热透镜现象的上升和衰减时间进行一些定量估计。发现早期探测信号衰减τ₁ = 149 ns与热透镜的上升时间τᵣ = 121 ns处于同一数量级。当考虑非线性散射时，得到的总衰减时间为τ = 1.8 μs。已通过实验确定热透镜的恢复时间为几十毫秒，这与理论值非常吻合。
