The laser-scanning confocal vibrometer microscope

Abstract

Sub-micrometer lateral resolution for the optical vibration measurement can be achieved when the scanned laser beam of a confocal microscope is the measurement beam of a heterodyne laser-Doppler vibrometer. Such a scanning system that allows vibration measurements up to 30 MHz is presented in this paper for the first time. We measured a minimum 2 / 1 e -power spot diameter of 745 nm and, therefore, the vibration analysis of sub-micrometer mechanical structures is possible with our system. We demonstrate measurements on comb-drive fingers with 2 µm diameter, the tiniest structures available for us.