Michelson Interferometer

Piezo Electric Effect

Michelson interferometer is a widely used instrument for measuring wavelength of light, refractive index of transparent materials etc. In Holmarc's Apparatus (Model No: HO-ED-INT-06P), Michelson Interferometer is used as 'Optical Ruler' to calculate the displacement factor of piezoelectric actuator in accordance with the Piezoelectric Effect. An applied voltage will cause a piezoelectric actuator to exhibit a tiny mechanical displacement(typically in nanometer).

The displacements are measured using the beam of light from a diode laser (650nm) in the Michelson Interferometer to calculate the minute motions. The applications of the Piezoelectric effect has reached almost every fields of science and technology, being utilized in advanced disciplines such as the atomic force microscopy, all forms of vibration suppression etc.

Holmarc's Michelson Interferometer-piezoelectric effect uses two mirrors in a Michelson arrangement to obtain the interference pattern. The interferometer is assembled with a Piezoelectric Actuator on a movable mirror. When the voltage across the Piezoelectric Actuator is increased from zero to maximum gradually, we can observe shift in the fringe pattern. One can determine the fringe shift and hence the displacement produced by the Piezoelectric Actuator can be calculated.

The instrument uses laser diode as light source. Assembly and alignment are easy to understand. Laser, mirrors and beam splitter are mounted on precision kinematic mounts for fine tuning and alignment. The interference fringes are obtained on a screen and can be viewed with naked eye. Due to the Piezoelectric Effect, one of the mirrors is shifted by the variation in the voltage applied to the sample, and the change in interference pattern is observed. Students can assemble the interferometer out of individual modules by fixing them on the optical breadboard. All components required for such assembly, including screws and allen keys, are supplied with the package.

Experiment:

   To observe the Piezo Electric Effect

   To obtain the displacement factor by counting the fringe shift

Features:

Piezo Electric Actuator:

Piezoelectric Actuators

A piezoelectric actuator converts an electrical signal into a precisely controlled physical displacement (stroke). If displacement is prevented, a useable force (blocking force) will develop. The precise movement control afforded by piezoelectric actuators is used to finely adjust machining tools, lenses, mirrors, or other equipment. Piezoelectric actuators are also used to control hydraulic valves, acting as small-volume pumps or special-purpose motors and in other applications requiring movement or force. When an electric field is applied across the material, the polarized molecules will align themselves with the electric field, resulting in induced dipoles within the molecular or crystal structure of the material. This alignment of molecules will cause the material to change dimensions. This phenomenon is known as electrostriction. This can be utilized by engineers to develop instruments for measuring exact displacement factors. They can use this knowledge to apply exact voltages and produce nanometer displacements with an incredibly small margin of error. Knowing this is immensely important, especially in the ever growing field of nano-technology, where the smooth movement of a piezo electric actuator would be able to move minute parts and manufacture tiny materials.