Title:	Sensitive measurement of absolute two-photon absorption cross sections
Authors:	Sengupta, P. Balaji, J. Banerjee, Subhashish Philip, Reji Kumar, G.R. Maiti, S.
Issue Date:	Jun-2000
Publisher:	American Institute of Physics
Citation:	Journal of Chemical Physics, 2000, Vol.112, p9201-9205
Abstract:	We develop a method for measuring absolute two-photon absorption cross sections (σ2) and employ it to determine the σ2 of Rhodamine-6G in methanol (16.2+/-2.4 GM at 806 nm). Our measurement calibrates the relative excitation spectrum previously reported for this chromophore. The method is based on our derivation of an analytical expression describing the transmission of Gaussian laser pulses through a two-photon absorbing medium. The expression is valid for arbitrary absorber thickness, at all distances from the focus. This generalizes the prevalent ``z-scan'' (translation of the sample along the beam direction) technique for measuring two-photon absorbance, removing the requirements of a ``thin'' (thickness << Rayleigh range of the focused laser beam) sample and of placing the sample at the focus. This leads to an improvement of the sensitivity of the technique by over two orders of magnitude, enabling measurement of the two-photon absorption cross sections of even weakly absorbing specimens at moderate intensities. The results are significant for applications such as nonlinear microscopy, optical data storage and optical power limiting.
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/4725
ISSN:	0021-9606 1089-7690
Alternative Location:	http://dx.doi.org/10.1063/1.481540 http://adsabs.harvard.edu/abs/2000JChPh.112.9201S
Copyright:	2000 American Institute of Physics
Appears in Collections:	Research Papers (LAMP)

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