Nanoscale vibrometric measurement apparatus and method

A method for measuring the surface motion of the surface of an object, comprising the steps of:

• (a) generating a source light having a wavelength;
• (b) providing an optical fiber having an input end and an output end, said output end including an aperture therein, said aperture having a diameter less than said source light wavelength;
• (c) positioning the output end of the optical fiber at a desired position relative to the surface of the sample;
• (d) inputting the source light into the input end;
• (e) transmitting the light from the aperture of the optical fiber toward the surface of the object;
• (f) providing a collection objective;
• (g) in the collection objective, collecting a direct component of the light transmitted from the aperture while collecting a Doppler-shifted light reflected from the surface of the object, said direct component and said Doppler-shifted reflected light thereby comprising two interfering beams that combine to form an interfered light signal having an intensity modulated by a relative phase shift between the direct component and the Doppler-shifted reflected light that is proportional to an out-of-plane displacement caused by the surface motion of said surface;
• (h) receiving and converting the interfered light signal to an electrical signal proportional to the intensity and representative of the amount of the surface motion of the object;
• (i) receiving and processing the electrical signal;
• and
• (j) outputting a measurement of the amount of surface motion of said surface.

A vibrometric measuring apparatus for measuring an amount of surface motion of a surface of an object, comprising:

• a light source for outputting a source light having a wavelength along an optical path;
• an optical fiber positioned in the optical path and comprising an input end for receiving the source light and a tapered tip output end including an aperture for emitting a fiber light output, said aperture having a diameter less than said source light wavelength;
• a collection objective positioned with respect to said aperture, so as to collect a direct component of the fiber light output, and positionable with respect to the object so as to collect a Doppler-shifted reflected light of the fiber light output from the surface of the object, said direct component of the fiber light output and said Doppler-shifted reflected light thereby comprising two interfering beams combining to form an interfered light signal having an intensity modulated by a relative phase shift between the two interfering beams that is proportional to an out-of-plane displacement caused by the surface motion of said surface;
• a photo-receiver comprising an input and an output, said input of said photo-receiver disposed for receiving and converting the interfered light signal to an electrical signal proportional to the intensity and representative of the amount of surface motion of the object;
• a signal processor comprising an input for receiving and processing the electrical signal and an output for indicating the amount of surface motion of said surface;
• a tip altitude control system for positioning the output end of the optical fiber relative to the surface of the sample tip altitude control system comprising a programmable computer for controlling the amount of desired movement and altitude relative to the surface of the sample of the output end of the optical fiber and means for positioning the tip in response to a control signal from the computer;
• and
• a movable stage for receiving and securing the object so as to enable measurements to be taken at a plurality of locations on the surface.