Optical interferometry is a technique where two or more light waves are combined to produce an interference pattern. This interference pattern can be measured to extract information on the light.
A Michelson interferometer is a tool used to produce interference between two beams of light. It is the most common design for optical interferometry and the first interferometer invented, by Albert Abraham Michelson in the late 19th century.
The Michelson interferometer works by splitting a beam of monochromatic light into two equal amplitude beams. One beam hits a fixed mirror and the other hits a movable mirror giving different beam lengths which converge on a detector screen giving an interference pattern.
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This technique allows wavelength of a light to be measured, the refractive index of transparent materials and small changes in length.
Michelson interferometers are relatively simple in operation, and possess the largest field of view for a specified wavelength. They also possess a relatively low temperature sensitivity.
The key applications of a Michelson interferometer are as follows:
- In the Michelson-Morley experiment, which led to the development of the special theory of relativity. This was a failed attempt to demonstrate a hypothetical “aether wind” as a theory of light.
- The detection of gravitational waves – LIGO is a massive interferometer with two lasers positioned thousands of kilometres apart
- In astronomical interferometry.
- In optical coherence tomography.
- In fibre optics.
- In analysing the upper atmosphere, by revealing temperatures and winds, and by measuring the Doppler widths and shifts in the spectra of airglow and aurora
- As a component in the helioseismic and magnetic imager to study solar variability, and to illustrate the Sun's interior, along with the many aspects of magnetic activity
- As a tunable narrow band filter
- As the core of Fourier transform spectroscopy