Near-Field Fluorescence Microscopy Based on Two-Photon Excitation with Metal Tips

Erik J. Sánchez; Lukas Novotny; X. Sunney Xie

doi:10.1103/PhysRevLett.82.4014

Near-Field Fluorescence Microscopy Based on Two-Photon Excitation with Metal Tips

Erik J. Sánchez, Lukas Novotny, and X. Sunney Xie

Phys. Rev. Lett. 82, 4014 – Published 17 May 1999

Abstract

We present a new scheme for near-field fluorescence imaging using a metal tip illuminated with femtosecond laser pulses of proper polarization. The strongly enhanced electric field at the metal tip ( $\approx 15 nm$ end diameter) results in a localized excitation source for molecular fluorescence. Excitation of the sample via two-photon absorption provides good image contrast due to the quadratic intensity dependence. The spatial resolution is shown to be better than that of the conventional aperture technique. We used the technique to image fragments of photosynthetic membranes, as well as $J$ -aggregates with spatial resolutions on the order of 20 nm.

Received 6 January 1999

DOI:https://doi.org/10.1103/PhysRevLett.82.4014

Authors & Affiliations

Erik J. Sánchez^1,2,*, Lukas Novotny^1,†, and X. Sunney Xie^1,2,‡

¹William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
²Department of Physics/Environmental Science and Resources Program, Portland State University, P.O. Box 751, Portland, Oregon 97207-0751

^*Present address: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138.
^†Present address: The Institute of Optics, University of Rochester, Rochester, New York 14627.
^‡Present address: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138.