title: Near-field scanning optical microscopy of single molecules by femtosecond two-photon excitation.
abstract: We present a demonstration of near-field scanning optical microscopy of single molecules based on ultrafast two-photon-induced fluorescence. Measurements were performed by use of 100-fs pulses at 800 nm from a Ti:sapphire laser to excite the two-photon transition in Rhodamine B molecules. Although near-field probes are normally metal coated to achieve superresolution, we used uncoated tips to achieve sufficiently high optical powers to generate acceptable fluorescence emission rates. Images of single molecules demonstrate a resolution of ~175nm(< lambda/4) on a topographically smooth surface, which surpasses the apparent lambda/2 resolution limit for uncoated tips operating in the linear response regime.
authors: M K
authors: MK
authors: Lewis
authors: P
authors: P
authors: Wolanin
authors: A
authors: A
authors: Gafni
authors: D G
authors: DG
authors: Steel