Question

Which optical interferometer do you like most. Describe the optical layout and the working of this interferometer including one application where it is used. Draw diagrams as needed

Answer 1

Michelson Interferometer - This is the most simple interferometer by far. It is based on interference of two beams basically.. The light from the laser is split into two parts (rays). One part goes towards mirror 1 and reflected back and the other part goes to mirror 2 and reflected back. The two parts again recombine at the splitter and get overlapped on a screen which will produce either a constructive or destructive interference. It is based on the principle that electromagnetic waves propagate in vacuum.

Here is the diagram ( I have made this diagram in MS paint)

In the above diagram, the compensator compensates for optical path length of the ray falling at mirror 1 because it doesn't passes through beam splitter so it optical path length is shorter than the other wave. The beam splitter is half silver coated and is at 45 degree angle.

In this, the constructive interference will happen when path length is integer number of wavelength

L = m

and destructive interference occurs when

L = (m + 1/2)

Applications

There are so many applications some of which are

1) The detection of gravitational waves – LIGO is a massive interferometer with two lasers positioned thousands of kilometres apart

2) In astronomical interferometry.

3) In fibre optics.