Nonlinear constant r | could be calculated according to the numbers of the diffraction rings . the sample ' s optical limiting properties were discussed . according to the experimental results , we estimated that the main mechanism of the optical limiting was from the thermo - optic effect 對2 -甲氧基5 -丁氧基取代ppv氯仿溶液進行了激光誘導自衍射實驗,根據衍射環的個數估算出了樣品的非線性常數;同時還對該樣品進行了光限幅特性的研究,由實驗結果分析得出:由光熱效應引起的自衍射是產生光限幅特性的主要機制。