Experimental results for the nonlinear optical properties of thin films of molecular J-aggregates of substituted pseudoisocyanine (PIC) are reported. These molecular aggregates were found to possess a giant third-order optical nonlinearity (jc 3 j % 10 À5 esu). Thin films of J-aggregates of PIC iodide with several different N-alkyl substituents were obtained to study the effect of disorder on the nonlinear optical properties. The spectral features of the nonlinear optical susceptibility are analyzed within a model that includes exciton±exciton interactions.

Nonlinear optical properties of one-dimensional organic molecular aggregates in nanometer films Markov, R.V.; Plekhanov, A.I.; Shelkovnikov, V.V.; Knoester, J. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractNanometer films of molecular J-aggregates of pseudoisocyanine (PIC) with various degrees of both static and dynamic disorder were prepared. The amount of static disorder was varied by modifying the local environment of the J-aggregates in the films, while the dynamic disorder was varied by changing the film temperature. Through these variations, the delocalization length N of the excitons was controlled, as could be monitored from the width of the exciton absorption del (3) line. This has allowed us to establish the scaling of the nonlinear optical susceptibility per aggregate molecule, x /N, with

When the gas particles, which can be considered as a two level quantum system, are affected by frequent collisions with buffer gas particles (thermal reservoir), the spectral densities of the Einstein coefficients for absorption and induced emission are unequal to each other far from the absorption (emission) line. The relationship between the spectral densities at the specified condition reveals new physical phenomena. The mostly convincing example is the fact that population inversion is established in a two level system under nonresonance optical excitation. This effect is experimentally observed as a lasing on sodium resonance transitions.

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