Abstract
We report spots of excited molecules of 33 nm width created with focused light of wavelength and conventional optics along the optic axis. This is accomplished by exciting the molecules with a femtosecond pulse and subsequent depletion of their excited state with red-shifted, picosecond-pulsed, counterpropagating, coherent light fields. The ratio constitutes what is to our knowledge the sharpest spatial definition attained with freely propagating electromagnetic radiation. The sub-diffraction spots enable for the first time far-field fluorescence microscopy with resolution at the tens of nanometer scale, as demonstrated in images of membranes of bacillus megaterium.
- Received 19 September 2001
DOI:https://doi.org/10.1103/PhysRevLett.88.163901
©2002 American Physical Society