Overview
A diffractive optical element (DOE), in general, is an optical element on which light can undergo diffraction to produce a predetermined pattern on the other side. Light takes multiple paths to arrive at each spot of light or dark and interferes with itself to produce the pattern. Our DOE is designed to produce a pattern of lines (in actuality these lines are collection of closely spaced points) which appear to diverge from a common focal point.
Tutorial
This element is used to separate the LASER beam into several beams of lines which are then used in the Ray Optics Experiment. Both LASER and DOE are assembled on separate tilt mounts which are then fixed to the optic table along a single mutual axis.
Mounting Options
The DOE comes fitted with a specially designed housing to easily affix the element to the tilt mount.
Theoretical Background
Diffraction and interference are byproducts of light’s superposition principle. That is, when one light wave meets another light wave, their amplitudes add up. If these waves are coherent then an interference pattern can be readily observed. When coherent waves are identical, nothing very interesting happens. It is only when the optical path each takes is distinct that interference becomes interesting.
For two coherent waves – that is, they have the same polarization and wavelength, as well as a constant phase difference between them – we can observe, mathematically, the effect of interference. Suppose two coherent waves of identical amplitudes but different starting locations are given:
We can mark each starting point as the starting phase:
Then, by the superposition principle
and the intensity can be shown to be:
Therefore, distinct phase differences:
have distinct effects on the total intensity:
which is how we get light and dark spots – or, in this case, lines.