Poking Around with Light at the Nanometer Scale

Dr. Jordan Gerton
Department of Physics
University of Utah

We have developed a technique called tip-enhanced fluorescence microscopy that utilizes the sharp tip from an atomic-force microscope to concentrate the optical intensity of a laser beam.  The intensity at the tip apex can be enhanced by more than a factor of ten compared to the peak laser intensity, and the enhancement region is strongly confined to within a few nanometers of the tip apex.  Thus, the tip induces a local increase in the optical excitation rate as it is scanned over a fluorescent sample, producing images with spatial resolution limited primarily by the sharpness of the tip (~10 nm).  This breaks the diffraction limit by a factor of ~30 for visible (600 nm wavelength) light!  I will describe the physics that enables this remarkable spatial resolution and discuss some measurements on semiconductor nanocrystal quantum dots and short pieces of DNA.  Further, I will discuss how carbon nanotubes can be used for nanometer-scale optical microscopy.  Finally, I will discuss our efforts for using this technique to study the nanoscale architecture of protein networks in biological membranes.  All efforts will be made to deliver this colloquium at a level accessible to undergraduate science majors.