The height regulation of a near-field scanning optical microscope probe tip

A nonoptical detection of the optical fibre tip has been developed. By detecting the output signal from a tiny piezoelectric detector attached to the vibrating fibre tip, the distance between the fibre tip and the sample has been successfully controlled. The frequency responses of the system composed of tip, the dither and the detector have been studied. The difference between the shear-force detect-ion and the tapping-mode detection is discussed. It is found that the shear force exerted on the tip reduces the vibration amplitude with an unvaried resonance frequency, However. in the tapping mode. the resonance frequency varies with the tip-sample distance as the force is exerted on the fibre tip only within a half period. This requires better adjustments for the tapping-mode detection.