Micro force Measurement by an Optical Method

摘要

We discuss the application of stress-induced changes in the crystal of a monolithic Nd: YAG laser as a possibility for micro force measurement. In fact, the application of an unknown force on the resonator-amplifier of a laser, formed by a transparent photo elastic material, can lead to a change of the laser frequency by as much as several gigahertz depending on the force intensity. In addition, the rates of change of the two orthogonally polarizations of the same mode with applied force are different. Hence, the strength of the applied force can be deduced from frequency measurement of the beat signal between the two polarizations of the oscillating mode or between the mode polarized in the orthogonal direction of the force and a reference frequency of a stabilized laser.