Refractive index database

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Optical constants of BeAl2O4 (Beryllium aluminate, chrysoberyl)
Walling et al. 1980: n(β) 0.25–2.6 µm

Wavelength: µm

Complex refractive index (n+ik)[ i ]

n   k   LogX   LogY   eV

Derived optical constants

Dispersion formula [ i ]



nβ; Room temperature.


1) J. Walling, O. Peterson, H. Jenssen, R. Morris, E. O'Dell. Tunable alexandrite lasers, IEEE J. Quantum Electron., 16, 1302–1315 (1980)
2) P. Loiko, A. Major. Dispersive properties of alexandrite and beryllium hexaaluminate crystals, Opt. Mater. Express, 6, 2177–2183 (2016)
* Ref. 2 provides a dispersion formula based on the experimental data from Ref. 1


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Beryllium aluminate, BeAl2O4

BeAl2O4, commonly known as chrysoberyl, is a beryllium-aluminum oxide mineral that is noteworthy for its excellent hardness and durability. In the field of optics, chrysoberyl is used mainly as a gemstone and is not often encountered in technical applications due to its high cost and relative scarcity. However, its natural form, known as "cat's eye," is a unique gemstone admired for its chatoyancy. While not commonly utilized in high-technology optical applications, the properties of chrysoberyl, such as its excellent thermal stability and high hardness, could theoretically make it valuable in extreme environments where other materials may fail. The crystal structure of BeAl2O4 contributes to its remarkable hardness, which is second only to diamond among naturally occurring materials. Overall, while not a mainstream choice for technical optics, chrysoberyl remains an intriguing material whose unique characteristics could inspire future research and applications in specialized optical contexts.

Other name

  • Beryllium aluminum oxide
  • Alexandrite (usually Cr3+:BeAl2O4)


  • Chrysoberyl

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