Nonlinear optical response of a novel polydiacetylene poly(1,4 bis(3-quinolyl)-1,3 butadyne): Role of exciton-phonon interaction
Department of Physics,
Indian Institute of Technology - Bombay, 400 076,
2 Department of Chemistry, Indian Institute of Technology - Bombay, 400 076, India
Accepted: 10 December 1998
A model incorporating the exciton-phonon interaction for a quantitative description of the third-order nonlinear optical response of a one-dimensional conjugated polymer chain in the vicinity of a one-photon resonance is proposed. This model has been used to describe our observations on the dispersion of the second molecular hyperpolarizability, , of poly(1,4 bis(3-quinolyl))-1,3 butadyne in the spectral range 720–810 nm satisfactorily. The large observed precipitous enhancement close to the absorption tail could not be explained by the essential states models. It is found that the phonon-mediated shift of the exciton resonance is responsible for the large monotonic variation of , whilst the phase space filling effect renders its self-defocusing character.
PACS: 42.65.An – Optical susceptibility, hyperpolarizability / 71.35.Lk – Collective effects (Bose effects, phase space filling, and excitonic phase transitions) / 71.35.Aa – Frenkel excitons and self-trapped excitons
© EDP Sciences, 1999