Controlling and tuning strong optical field gradients at a local probe microscope tip apex

We show that strong optical field gradients can be created at the tip apex of a local probe microscope illuminated by an external light source. We demonstrate that these confined fields can be easily, precisely and continuously tuned by changing the polarization and the incidence of the external field. We also investigate the topology of the field intensity in the tip-surface junction. (C) 1997 American Institute of Physics.