We report that the stimulated Raman gain signals of a single-crystal polydiacetylene with the side groups2, 5-bis-trifluoromethyl-phenyl, PDA-DFMP, exhibit an optical Stark shift of ==50 cm-1. Using an ultrashort, near-resonant high-intensity laser, we find that te intensity-dependent signal shifts to higher probe photonenergies for both the C=C- and C=C-stretching modes. Semiquantitative agreement between the dataand a three-level-system density-matrix calculation is achieved with a nonlinear-optical mechanism in whicha pump-laser field is optically coupled to both the exciton ← zero-phonon ground-state and the excit←ononephonon ground-state transitions.
|Number of pages
|Journal of the Optical Society of America B: Optical Physics
|Published - 1994 May