DeepLightSeekdefinition:
A transparent optical device that can refract or reflect light.
An optical prism is a transparent device in which light can propagate, typically made of glass. Due to the fact that the end faces are not parallel to each other, refraction occurs (the direction of the beam changes), and due to the dispersion of the material, refraction is usually wavelength dependent.
However, sometimes total reflection is required, and sometimes the direction of the outgoing beam is independent of the wavelength.
The reflected light on the surface of the prism needs to be eliminated. When the light is P-polarized and the incident angle is Brewster angle, the reflected light can be suppressed. Sometimes anti reflective coatings are also used to eliminate reflected light.
Prisms are needed in many aspects of optics; Below will provide some examples.
Dispersive prism
When a laser beam propagates in a prism, the two end faces of the prism are not parallel, so the beam will deviate, and the deviation angle is related to the refractive index. Due to the dispersion of materials, the deflection angle is also wavelength dependent. This is a dispersive prism, used for the following purposes: 
Figure 1: Prisms separate different wavelength components in space while introducing wavelength dependent phase changes and dispersion.
Usually, it is not desirable to change the beam size. It is easy to arrange prisms in a symmetrical structure, and the deflection angle is minimized at this time.
For example, using high dispersion flint glass SF10 to make a prism, it is very suitable to make the prism into an equilateral triangle because the incident angle and exit angle are approximately symmetrical, with an angle close to the Brewster angle of about 60 °.
Retroreflector prism 
Figure 2: Backward reflecting prism. Even if the prism is slightly tilted, the direction of the reflected light remains unchanged.
A right angled prism can be used as a retroreflector, which utilizes total reflection at two positions (Figure 2). If the angle between two reflective surfaces is 90 °, the resulting reflected beam is parallel to the incident beam, even if the prism is slightly tilted. Just the beam offset will change.
If the mirror is tilted, the angle at which the beam direction changes is twice the tilt angle. The retroreflector prism is easy to arrange because its specific orientation is not closely related.
In this structure, the refraction at the incident/exit interface is wavelength dependent and does not have an impact, as the beam is almost perpendicular to the surface.
Distorted prism
Figure 3: Distortion prism. The outgoing beam is much narrower than the incoming beam.
Distortion prism can change the beam size in one direction. At this point, there is a significant difference in the angle between the incident light and the corresponding surface, for example, in Figure 3, the incident beam is perpendicular to the surface.
At this point, the beam size only changes in one direction, which is caused by the structure rather than focusing or other mechanisms.
Due to at least one beam being far from the Brewster angle, it is often necessary to use anti reflective coatings to eliminate reflections.
If there is no need to change the direction of the beam, a pair of prisms can be used to obtain a beam with only horizontal deviation.
The typical application of a distorted prism is to make the output beam of a laser diode symmetrical. Distortion prisms are usually used to keep the direction of the beam unchanged.
Composite prism
A composite prism is obtained by combining two or more prisms of different materials together. For example, a prism has a total offset angle of 0 caused by the refraction of the inner surface, but the beam offset is wavelength dependent. This can be used in low resolution spectrometers.
Prism polarizer
Polarizers are typically obtained from prisms, such as Glan Taylor prisms and Wollaston prisms. Refer to the polarizer for more details.
A transparent optical device that can refract or reflect light.
An optical prism is a transparent device in which light can propagate, typically made of glass. Due to the fact that the end faces are not parallel to each other, refraction occurs (the direction of the beam changes), and due to the dispersion of the material, refraction is usually wavelength dependent.
However, sometimes total reflection is required, and sometimes the direction of the outgoing beam is independent of the wavelength.
The reflected light on the surface of the prism needs to be eliminated. When the light is P-polarized and the incident angle is Brewster angle, the reflected light can be suppressed. Sometimes anti reflective coatings are also used to eliminate reflected light.
Prisms are needed in many aspects of optics; Below will provide some examples.
Dispersive prism
When a laser beam propagates in a prism, the two end faces of the prism are not parallel, so the beam will deviate, and the deviation angle is related to the refractive index. Due to the dispersion of materials, the deflection angle is also wavelength dependent. This is a dispersive prism, used for the following purposes:
- It is possible to separate the components with significant wavelength differences in the light beam. For example, a frequency doubled beam can be separated from the fundamental light. It can also be used in spectrometers, but the wavelength resolution is lower because the angular dispersion is relatively small.
- Similarly, two different wavelengths of light can be combined into a beam (see spectral beamforming technique). If the two wavelengths are close, using a diffraction grating is more suitable because the grating has a higher angular dispersion resolution
- The lens inside the laser cavity can be used for wavelength tuning.
- Dispersion prisms not only generate dispersion of prism materials, but also the entire device's path is wavelength dependent (as shown in Figure 1).
- This method can be used for dispersion compensation in mode-locked lasers. Even if the prism dispersion is normal dispersion, anomalous dispersion can still be obtained.
Usually, it is not desirable to change the beam size. It is easy to arrange prisms in a symmetrical structure, and the deflection angle is minimized at this time.
For example, using high dispersion flint glass SF10 to make a prism, it is very suitable to make the prism into an equilateral triangle because the incident angle and exit angle are approximately symmetrical, with an angle close to the Brewster angle of about 60 °.
Retroreflector prism
A right angled prism can be used as a retroreflector, which utilizes total reflection at two positions (Figure 2). If the angle between two reflective surfaces is 90 °, the resulting reflected beam is parallel to the incident beam, even if the prism is slightly tilted. Just the beam offset will change.
If the mirror is tilted, the angle at which the beam direction changes is twice the tilt angle. The retroreflector prism is easy to arrange because its specific orientation is not closely related.
In this structure, the refraction at the incident/exit interface is wavelength dependent and does not have an impact, as the beam is almost perpendicular to the surface.
Distorted prism
Distortion prism can change the beam size in one direction. At this point, there is a significant difference in the angle between the incident light and the corresponding surface, for example, in Figure 3, the incident beam is perpendicular to the surface.
At this point, the beam size only changes in one direction, which is caused by the structure rather than focusing or other mechanisms.
Due to at least one beam being far from the Brewster angle, it is often necessary to use anti reflective coatings to eliminate reflections.
If there is no need to change the direction of the beam, a pair of prisms can be used to obtain a beam with only horizontal deviation.
The typical application of a distorted prism is to make the output beam of a laser diode symmetrical. Distortion prisms are usually used to keep the direction of the beam unchanged.
Composite prism
A composite prism is obtained by combining two or more prisms of different materials together. For example, a prism has a total offset angle of 0 caused by the refraction of the inner surface, but the beam offset is wavelength dependent. This can be used in low resolution spectrometers.
Prism polarizer
Polarizers are typically obtained from prisms, such as Glan Taylor prisms and Wollaston prisms. Refer to the polarizer for more details.
