Detecting nanometric vibrations of a liquid surface by a metal-coated fiber tip

Optical radiation emitted from a metal-coated fiber tip apex when it emerges from a liquid into the air was measured. A strong enhancement of the output radiation and its strong dependence on the relative position of the tip to a liquid surface were observed. This phenomenon permits in situ recording of nanometric vibrations of the liquid and provides a basis for development of various ultrasensitive vibration detecting sensors.