Uniaxial Crystal Vs Biaxial Crystal | Difference between Uniaxial Crystal and Biaxial Crystal
This page compares Uniaxial Crystal vs Biaxial Crystal and mentions difference between Uniaxial Crystal and Biaxial Crystal. It mentions comparison between positive Uniaxial Crystal and negative Uniaxial Crystal types and their uses.
• This crystal is described by one optical axis and two principal refractive indices.
• Examples of uniaxial Crystals are calcite, KDP, quartz, rutile etc.
• When light beam passes through such crystal, it splits into o-ray and e-ray >>. Here o-ray passes through it without any deviation where as e-ray deviates at air to crystal interface.
• There are two forms of uniaxial crystals viz. positive uniaxial crystal and negative uniaxial crystal.
Positive Uniaxial crystal vs Negative Uniaxial crystal
• When light is propagated through uniaxial crystal the wavefronts (i.e. Huygen's wave surfaces)
due to o-ray and e-ray are depicted as shown in the figure-1. Based on relative velocities of o-ray and e-ray following two
cases may arise.
• Case-1: If Vo > Ve (i.e. no < ne) in all the directions except along optical axis. In this case, spherical wavefront due to o-ray would be outside of elliptical wavefront due to e-ray. In this condition, two wavefronts from o-ray and e-ray touch only at two diametrically opposite points on the optical axis. Such crystals are known as positive uniaxial crystals. Examples of such crystals are quartz, rutile etc.
• Case-2: If Vo < Ve (i.e. no > ne), the elliptical wavefront due to e-ray is outside of the spherical wavefront due to o-ray. Such crystals are known as negative uniaxial crystals. Examples of such crystals are calcite, KDP etc. Double refraction properties in such birefringent crystals depend on following three factors.
-Polarization state of incoming light ray
-Incidence angle of light ray
-Orientation of crystal's optical axis with respect to its surface plane etc.
• This crystal is described by two optical axis and three principal refractive indices.
• Examples of biaxial Crystals are mica, lead oxide, topaz etc.
• These crystals are also known as birefringent crystals.
• When light beam passed through this crystal, it splits into two parts. Both the fractions are e-rays. These waves or rays have different directions and speeds.
• Examples: Crystalline structures e.g. orthorhombic or monoclinic or triclinic etc.
Difference between Uniaxial Crystal and Biaxial Crystal
Table has been derived from differencebetween.com website. Refer difference between uniaxial and biaxial crystals >> for more information.