Polarization rotator
Encyclopedia
A polarization rotator is an optical device that rotates the polarization axis of a linearly polarized
light beam by an angle of choice. These rotators are either based on the principle of birefringence
or on total internal reflection
.
Half-wave plates and quarter-wave plates: these rotators work due to the principle of birefringence
. Their performance is wavelength specific; a fact that may be a limitation. Switchable wave plates can also be manufactured out of liquid crystals or ferro-electric liquid crystals. These devices can be used to rapidly change the angle of polarization in response to an electric signal.
Double Fresnel rhomb
: rotates the linear polarization axis by 90 degrees. Works on total internal reflection and it uses four internal reflections. A disadvantage may be a low ratio of useful optical aperture to length.
Broadband prismatic rotator: rotates the linear polarization by 90 degrees. Works on total internal reflection and it uses seven internal reflections to induce collinear rotation. The term broadband indicates that the rotation is independent of wavelength, or achromatic.
Rotators of linearly polarized light have found widespread applications in modern optics since laser
beams tend to be linearly polarized and it is often necessary to rotate the original polarization to its orthogonal alternative.
Linear polarization
In electrodynamics, linear polarization or plane polarization of electromagnetic radiation is a confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation...
light beam by an angle of choice. These rotators are either based on the principle of birefringence
Birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...
or on total internal reflection
Total internal reflection
Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is...
.
Half-wave plates and quarter-wave plates: these rotators work due to the principle of birefringence
Birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...
. Their performance is wavelength specific; a fact that may be a limitation. Switchable wave plates can also be manufactured out of liquid crystals or ferro-electric liquid crystals. These devices can be used to rapidly change the angle of polarization in response to an electric signal.
Double Fresnel rhomb
Fresnel rhomb
A Fresnel rhomb is a prism-like device designed in 1817 by Augustin-Jean Fresnel for changing the polarization of light waves to be circularly polarized. Though the result is similar to that of using a wave plate, the rhomb does not depend on birefringent properties of the material...
: rotates the linear polarization axis by 90 degrees. Works on total internal reflection and it uses four internal reflections. A disadvantage may be a low ratio of useful optical aperture to length.
Broadband prismatic rotator: rotates the linear polarization by 90 degrees. Works on total internal reflection and it uses seven internal reflections to induce collinear rotation. The term broadband indicates that the rotation is independent of wavelength, or achromatic.
Rotators of linearly polarized light have found widespread applications in modern optics since laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
beams tend to be linearly polarized and it is often necessary to rotate the original polarization to its orthogonal alternative.