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Birefringence: The phenomenon in terms of polarization, understanding light as a wave with field components in transverse polarizations (perpendicular to the direction of the wave vector).
A crystal with its optic axis in this orientation, parallel to the optical surface, may be used to create a waveplate, in which there is no distortion of the image but an intentional modification of the state of polarization of the incident wave.
For instance, a quarter-wave plate is commonly used to create circular polarization from a linearly polarized source.
Similarly, light modulators modulate the intensity of light through electrically induced birefringence of polarized light followed by a polarizer.
Birefringence can be observed in amyloid plaques such as are found in the brains of Alzheimer’s patients when stained with a dye such as Congo Red.
In ophthalmology, scanning laser polarimetry utilises the birefringence of the optic nerve fibre layer to indirectly quantify its thickness,
The study of birefringence in shear waves traveling through the solid earth is widely used in seismology. Birefringence is widely used in mineralogy to identify rocks, minerals, and gemstones.
Birefringence results when a material’s permittivity is not describable using a scalar value, but requires a tensor to relate the electric displacement (D) with the electric field (E). Continue reading →