Editing Birefringence (section)

===Optical devices===
Birefringence is used in many optical devices. [[Liquid-crystal display]]s, the most common sort of [[flat-panel display]], cause their pixels to become lighter or darker through rotation of the polarization (circular birefringence) of linearly polarized light as viewed through a sheet polarizer at the screen's surface. Similarly, [[electro-optic modulator|light modulators]] modulate the intensity of light through [[Pockels effect|electrically induced birefringence]] of polarized light followed by a polarizer. The [[Lyot filter]] is a specialized narrowband spectral filter employing the wavelength dependence of birefringence. [[Waveplate]]s are thin birefringent sheets widely used in certain optical equipment for modifying the polarization state of light passing through it.

To manufacture polarizers with high transmittance, birefringent crystals are used in devices such as the [[Glan–Thompson prism]], [[Glan–Taylor prism]] and other variants.<ref name="Home f364">{{cite web | title=Birefringent_ Polarizers | website=Home | url=https://www.pmoptics.com/birefringent_polarizers.html | access-date=2024-03-15}}</ref> Layered birefringent polymer sheets can also be used for this purpose.<ref name="Gilbert Weber Strharsky Stover 2001 p. FA2">{{cite conference | last1=Gilbert | first1=Larry | last2=Weber | first2=M.F. | last3=Strharsky | first3=R.J. | last4=Stover | first4=C.A. | last5=Nevitt | first5=T.J. | last6=Ouderkirk | first6=A.J. | title=Optical Interference Coatings | chapter=Giant birefringent optics in multilayer polymer filters | publisher=OSA | date=2001 | isbn=978-1-55752-682-3 | doi=10.1364/OIC.2001.FA2 | page=FA2}}</ref>

Birefringence also plays an important role in [[second-harmonic generation]] and other [[Nonlinear optics|nonlinear optical processes]]. The crystals used for these purposes are almost always birefringent. By adjusting the angle of incidence, the effective refractive index of the extraordinary ray can be tuned in order to achieve [[Nonlinear optics#Phase matching|phase matching]], which is required for the efficient operation of these devices.