Editing Birefringence (section)

===Stress-induced birefringence===
[[Image:Birefringence Stress Plastic.JPG|left|thumb|250px|Color pattern of a plastic box with "frozen in" [[mechanical stress]] placed between two crossed [[polarizer]]s]]
[[Isotropic]] solids do not exhibit birefringence. When they are under [[mechanical stress]], birefringence results. The stress can be applied externally or is "frozen in" after a birefringent plastic ware is cooled after it is manufactured using [[injection molding]]. When such a sample is placed between two crossed polarizers, colour patterns can be observed, because polarization of a light ray is rotated after passing through a birefringent material and the amount of rotation is dependent on wavelength. The experimental method called [[photoelasticity]] used for analyzing stress distribution in solids is based on the same principle. There has been recent research on using stress-induced birefringence in a glass plate to generate an [[optical vortex]] and full Poincare beams (optical beams that have every possible polarization state across a cross-section).<ref>{{Cite journal|last1=Beckley|first1=Amber M.|last2=Brown|first2=Thomas G.|last3=Alonso|first3=Miguel A.|date=2010-05-10|title=Full Poincaré beams|url=https://www.osapublishing.org/abstract.cfm?uri=oe-18-10-10777|journal=Optics Express|language=EN|volume=18|issue=10|pages=10777–10785|doi=10.1364/OE.18.010777|pmid=20588931|issn=1094-4087|bibcode=2010OExpr..1810777B|doi-access=free}}</ref>
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