  We present a near-field optical technique for second harmonic imaging using
bare tapered optical fiber tip illuminated with femtosecond laser pulses.
Enhancement of electric field at the tip of the fiber results in enhanced
second harmonic generation (SHG) from the sample region near the tip. This SH
emission is collected by the same tapered fiber. Spatial distribution of SHG
from thin ferroelectric Pb(Zr_xTi_1-x)O_3 films and model metal-ferroelectric
devices has been studied. Spatial resolution on the order of 80 nm has been
achieved. This is the first time diffraction limit is surpassed in SH
microscopic measurements. Electric field induced changes in SHG from individual
grains and/or domains of ferroelectric thin films have been observed.
