Abstract: A perpendicular-mode near-field scanning optical microscope (NSOM) utilizing a piezoelectric micro tuning fork as its height-sensing element is described. The present invention provides a method and apparatus for modifying and attaching an optical fiber to the tuning fork that allows the assembly to retain Q-factors up to 9000, substantially higher than those described so far in the literature for tuning-fork-based instruments. The method involves reducing the diameter of the cladding of the optical fiber down to the 17-25 &mgr;m using several chemical etching steps, before the fiber is attached to the tuning fork. A sharp upturn in the Q-factor is observed when the fiber diameter d drops below ˜25 &mgr;m. An analysis, which shows that the stretching force constant of a bent fiber is proportional to d4, is used to account for the great sensitivity of the Q-factor to the fiber diameter.