A COMPARATIVE STUDY OF C60, PTHALOCYANINE, AND PORPHYRIN FOR OPTICAL LIMITING OVER THE VISIBLE REGION
A COMPARATIVE STUDY OF C60, PTHALOCYANINE, AND PORPHYRIN FOR OPTICAL LIMITING OVER THE VISIBLE REGION
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C60、酞菁和卟啉在可见光区域光学限制的比较研究
DOI：
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发表时间：
1998
影响因子：
0.6
通讯作者：
J. Akkara
中科院分区：
文献类型：
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作者：
D. N. Rao;E. Blanco;Venugopal Rao Soma;F. Aranda;D. Rao;S. Tripathy;J. Akkara
前言光学限幅器是一种在高强度下强烈衰减光束，而在低强度下表现出高透过率的器件。这种装置是保护人眼和光学传感器免受强激光照射所必需的。人们正在加紧寻找具有这种特性的材料。这些材料的开发基于各种机制，例如半导体中的非线性吸收和折射、碳颗粒悬浮液中的光学击穿诱导散射2、热折射光束扩散3和激发态吸收“(有关光限幅机制的完整综述，请参阅L.W.Tutt et a/.S的文章)。最近的研究表明，在C60中表现出非常高的激发态吸收(ESA)或反饱和吸收(RSA)行为。6)、卟啉7和酞菁1。所有系统在532 nm处都有较高的激发态截面(0q)，并表现出RSA行为。由于系间交叉和三重态T1-Tn吸收的参与，ns激光脉冲激发导致RSA(0：：)增强。早期关于RSA的报道大多使用单一波长，即532或600 nm。我们在这里报道了激发态吸收。作者用Z-scan9实验对C60‘-酞菁和卟啉在可见光区的截面进行了测量。零扫描是一种单光束技术，在这种技术中，激光束被紧密聚焦，样品在焦平面上平移。开孔Z扫描用于监测样品相对于焦平面的归一化透过率与位置的关系。样品的位置与模具强度和注量有关。光功率限制的基本要求是系统必须表现出与通量相关的RSA 1°，C60‘-酞菁，以及卟啉具有比基态凝视吸收截面更大的激发态截面，因此它们是限制应用的合适候选者。
Introduction Optical limiters are devices that strongly attenuate optical beams at high intensities while exhibiting high transmittance at low intensities. Such devices are required for the protection of human eye and optical sensors from intense laser fields. There is an intense search for materials exhibiting such properties. The development of these materials is based on various mechanisms such as nonlinear absorption and refraction in semiconductors', optical breakdown-induced scattering in carbon particle suspensions2, thermal refractive beam spreading3 and excited state absorption" (for a complete review of mechanisms responsible for optical limiting, see article by L.W.Tutt et a/.S). Recent studies show very high performance excited state absorption (ESA) or reverse saturable absorption (RSA), behavior in C60 (Ref. 6), porphyrins7, and pthalocyaninesl. All the systems have higher excited state cross-sections (0 Q) at 532 om and show RSA behavior. Excitation with ns laser pulses leads to an enhanced RSA (0::) due to intersystem crossing and the involvement of triplet states T 1 to Tn absorption. Earlier reports on RSA are mostly using a single wavelength, i.e. 532 om or 600 om. We report here the excited state absorption . Author for colTe8\X!ndence cross-section for C60' pthalocyanine, and porphyrin using Z-scan9 experiment over the visible region. Zscan is a single beam technique in which a laser beam is tightly focused and the sample is translated across the focal plane. Open aperture Z-scans, where dIe total energy trnnsmitted through the sample is collected by a detector, are used to monitor the normalized transmittance vs position of the sample with respect to the focal plane. The sample position is related to dIe intensity and fluence. The fundamental requirement for optical power limiting is that the system must exhibit fluence dependent RSA 1°, C60' pthalocyanine, and porphyrin possess a larger excited state cross-section than the ground stare absorption cross-section and hence they are suitable candidates for limiting applications.