Nanoscale vibrometric measurement apparatus and method

摘要

An apparatus for measuring the amount of motion of the surface of a microscopic object includes a light source, an optical fiber for transmitting the light, and a collection objective. The optical fiber emits the light output through an aperture tapered to a diameter in the range of from 20 nm to 200 nm. The collection objective is positioned to receive both the direct component of the fiber light output and the Doppler-shifted reflected light of the fiber light output from the surface of the object. The direct component and the Doppler-shifted reflected light combine in the collection objective to form an interfered light signal that is output to a photo-receiver. The intensity of the interfered light signal is modulated by the relative phase shift between the two interfering beams and is proportional to the out-of-plane displacement caused by the surface motion of the object surface. The photo-receiver receives the interfered light signal and converts it to an electrical signal that is proportional to the light intensity and representative of the amount of the surface motion of the object. A signal processor processes the electrical signal and outputs the amount of surface motion of the object's surface. A tip altitude control system positions the output end of the optical fiber relative to the surface of the sample. A movable stage receives and secures the object in order to enable measurements to be taken at a plurality of locations on the surface of the object. In addition to measuring surface motion and detecting small mass changes on an object's surface, the invention may be used to measure high frequency surface phonons.