Refractive index database

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Optical constants of CRYSTALS
Quartz (SiO2)

Wavelength: µm

Complex refractive index (n+ik)[ i ]

n   k   LogX   LogY   eV

Derived optical constants

Dispersion formula [ i ]


Conditions & Spec sheet

n_is_absolute: false
wavelength_is_vacuum: false
temperature: 20 °C


Fused silica, 20 °C


1) I. H. Malitson. Interspecimen comparison of the refractive index of fused silica, J. Opt. Soc. Am. 55, 1205-1208 (1965)
2) C. Z. Tan. Determination of refractive index of silica glass for infrared wavelengths by IR spectroscopy, J. Non-Cryst. Solids 223, 158-163 (1998)
* Sellmeier formula is reported in Ref. 1 for the 0.21-3.71 μm wavelength range. Ref. 2 verifies the validity of the formula up to 6.7 μm.


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Silicon dioxide, SiO2

Silicon dioxide (SiO2), commonly known as silica, is found naturally in several crystalline forms, the most notable being quartz. Additionally, when silicon dioxide is manufactured without the crystalline structure, it forms what is known as fused silica. Fused silica is a non-crystalline (or amorphous) form of silicon dioxide and is produced by melting high purity silica at extremely high temperatures. It has superior optical clarity, especially in the ultraviolet (UV) range, and is resistant to thermal shock, making it valuable for many high-end optical applications, including lenses and windows in spacecraft and satellites. SiO2 is extensively used in electronics as an insulator and serves as a primary ingredient in the production of glass. It's also used in thin-film optics, often as antireflection coatings on optical devices. Beyond its optical applications, silicon dioxide finds use in ceramics, construction, and even as a food additive.

Other names

  • Quartz
  • Silica
  • Silicon oxide
  • Silicon(IV) dioxide


  • Alpha quartz (α-quartz, most common)
  • Beta quartz (β-quartz, only stable at temperatures above 573 °C)
  • Tridymite
  • Cristobalite
  • Coesite
  • Stishovite
  • Lechatelierite
  • Chalcedony

External links


Crystals are highly ordered, periodic structures that offer a range of unique optical properties unattainable with amorphous materials like glass. Comprising atoms, ions, or molecules arranged in a repeating lattice structure, crystals can be engineered or selected to exhibit specific characteristics such as high refractive indices, low dispersion, and even nonlinear optical behavior. Commonly used optical crystals include quartz, sapphire, and various synthetic materials like potassium titanyl phosphate (KTP) and lithium niobate (LiNbO3). These materials are often used in applications that require high levels of precision and performance, such as in laser systems, optoelectronic devices, and frequency converters. Crystals can also demonstrate phenomena like birefringence, where the refractive index varies depending on the polarization and direction of light, making them invaluable in specialized optical components like waveplates and polarizers. Advanced crystal structures like photonic and plasmonic crystals can manipulate light at the nanoscale, offering avenues for research and application in areas like integrated optics and quantum computing. It's important to note that the optical properties of crystals, such as their refractive index and absorption coefficients, can be highly anisotropic and dependent on the crystal orientation. Therefore, specific data must be consulted for precise applications. Overall, crystals offer a broad palette of options for manipulating light, making them integral to both classical and cutting-edge optical technologies.

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