Abstract
We report the three-dimensional imaging of the vibrational, solvent, orientational, and electronic relaxation in organic fluorescent samples at 200-500 nm spatial resolution. This is achieved in steady-state recordings by exciting the fluorophore with a femtosecond pulse and subsequent quenching with a time-delayed, redshifted femtosecond pulse through stimulated emission. Temporal resolution of 380 fs is solely determined by the pulse widths and is further reducible. Images of submicron structures revealing vibrational and solvent relaxation gradients are shown. Furthermore, we introduce contrast modes based on stimulated emission depletion and apply them to cellular imaging. (C) 2000 American Institute of Physics. [S0003- 6951(00)03727-X].