Wollaston prism is a kind of deflection prism, which is widely used in lithography lighting, dual-frequency laser interferometer, and other precision processing, measurement, and other fields. It can generate two beams of linearly polarized light separated from each other and whose vibration directions are perpendicular to each other, which is composed of two right-angle prisms glued together. The prism material is mostly calcite.
In the picture below, the material used is calcite. The optical axes of the two prisms are perpendicular to each other. When natural light is incident perpendicularly to the AB surface, the o light and e light travel in the same direction without refraction but travel at different speeds Vo and Ve respectively. When they enter the second prism successively since the optical axis of the second prism is perpendicular to the optical axis of the first prism, the o light in the first prism becomes e light for the second prism, and the e light becomes For o light. Therefore, the o-light originally in the first prism is refracted at the interface between the two prisms with the relative refractive index ne/no, while the e-light originally in the first prism is refracted with the relative refractive index no/ne. Because calcite is a negative crystal (no>ne), the e-ray in the second prism propagates away from the normal line of the interface between the two calcites, and the o-ray in the second prism propagates close to the normal line of the interface between the two calcites. As a result, the two beams of light are separated in the second prism. In this way, the Wollaston prism is refracted again by the rightmost surface and emitted by the Wollaston prism is two beams of polarized light separated by a certain angle, and their vibration directions are perpendicular to each other. When the apex angle of the prism (ie <1 in the figure) is not too large, the two refracted lights are separated almost symmetrically.
The angle between them is approximately φ=arcsin[(no-ne)tan<1].
The material of the Wollaston prism can also be quartz, but the angle between the two separated beams is much smaller. When the incident light is not monochromatic light, the two linearly polarized lights have a slight dispersion.
The chemical composition of calcite is calcium carbonate, and many small square pieces will be obtained by hitting calcite. This is also the source of its name “calcite”.
It can produce two beams of linearly polarized light that are separated from each other and whose vibration directions are perpendicular to each other. This principle requires a first understanding of the term birefringence.
Wollaston prism: An optical device that can produce two separate, linearly polarized lights whose vibration directions are perpendicular to each other. It is composed of two right-angle prisms, which are bonded with glycerin or castor oil.
Polarizing prisms are deflection devices made using the phenomenon of crystal birefringence. The Wollaston prism introduced here is one of them. The other common ones include Wola prisms and Nicol prisms.
When a very thin beam of natural light is incident perpendicularly to the AB surface, the o-light and e-light generated by the first prism are not separated but proceed at different speeds. Since the optical axis of the second prism is rotated by 90° relative to the first prism, the o-light and e-light are converted at the interface AC. The o-ray in the first prism becomes e-ray in the second prism. Because of the no>ne of calcite, the o light enters the optically dense medium from the optically dense medium when passing through the interface, so it will travel away from the normal line of the interface; while the e-light passes through the interface from the optically thinner medium into the optically dense medium, so it will approach The interface normal propagates, and as a result, the two beams are separated in the second prism. In this way, the two beams of linearly polarized light that are separated by a certain angle and whose light vectors are perpendicular to each other are refracted by the Wollaston prism again after being refracted by the CD surface.