Using a near-field-scanning-microscopy (NSOM) fiber tip, which can have a mode as small as about 50nm, SEA TADPOLE can resolve even the finest details of a tightly focused pulse.

This effect was predicted in the 1990s, but it was thought that it would never actually be observed. However, SEA TADPOLE can easily perform such measurements.  For more, see Bowlan, et al.