Theoretical investigation of carrier envelope phase dependence of all-optical poling with the third- and higher-order nonlinear processes.

Dependence of efficiency in all-optical poling with nonlinear processes, up to eighth order, is considered. The explicit form of the nonlinear susceptibility that is responsible for the poling is derived, which shows both CEP and phase mismatch dependence. On the basis of an analysis of pulse propagation in a nonlinear material, it is shown that one can identify the order of nonlinearity that is relevant to the poling process, relying on current technology of CEP stabilization and thin-film growth.

Exciton energy transfer between optically forbidden states of molecular aggregates.

3-ethyl-2-[3-(3-ethyl-2(3H)-benzoxazolylidene)-1-propenyl]benzoxazolium iodide (dye I) and pseudoisocyanine bromide are employed to form H aggregates as donors and J aggregates as acceptors. The energy of an H band of the H aggregates is higher than that of a J band of the J aggregates. It was confirmed that excitation of the H band does not emit fluorescence by comparison of excitation spectra of dye I H aggregates with that of dye I monomer. Absorption, fluorescence, and excitation spectra of spin-coated films of H aggregates mixed with various quantities of J aggregates have been observed. Excitation spectra probed at the J band are found to have a component of the H band. Fluorescence spectra originated from excitation of the H band are extracted and qualitatively analyzed. It is confirmed that excitation of the H band causes to emit fluorescence of a J band of the J aggregates. These phenomena show that exciton energy can transfer from the lowest energy in electronic states of the H aggregate, which state is optically forbidden, to electronic state of the J aggregate.