Refractive index database

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Optical constants of BGG (barium gallogermanate) glass
Zelmon et al. 2002: n 0.4–5.0 µm

Wavelength: µm

Complex refractive index (n+ik)[ i ]

n   k   LogX   LogY   eV

Derived optical constants

Dispersion formula [ i ]



BaO : Ga2O3 : GeO2 = 42.9 : 17.0 : 40.1.


D. E. Zelmon, S. S. Bayya, J. S. Sanghera, I. D. Aggarwal. Dispersion of barium gallogermanate glass, Appl. Opt. 41, 1366 (2002)


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Barium gallogermanate (BGG) glass

BGG glass, a member of the heavy crown glass family, is distinguished by its high refractive index and moderate optical dispersion. These characteristics make it an appealing choice for specialized optical systems that demand precise control over chromatic aberrations or a specific focal length. Due to its high refractive index, BGG glass enables the design of shorter focal lengths or smaller optical elements, potentially leading to more compact and lightweight optical systems. Commonly found in the catalogs of industry standards like Schott Glass, the BGG classification serves as a shorthand to convey key optical properties of the glass. As such, BGG glass is often employed in high-end camera lenses, scientific instruments, and other applications requiring exceptional optical performance. Its unique attributes make it an invaluable resource for optical designers striving for excellence in imaging and light manipulation.


BaO : Ga2O3 : GeO2


Glass is a versatile, amorphous material that has been an essential component in optical technologies for centuries. Comprising mainly of silica along with various additives like soda, lime, or boron, glass can be engineered to exhibit a wide range of optical properties, such as refractive indices and dispersion characteristics. In the optical industry, specialized types of glass like crown, flint, and extra-low dispersion (ED) glasses are used for manufacturing lenses, prisms, and other optical elements. These glasses are precisely formulated to offer specific properties, such as low chromatic aberration or high light transmittance across different spectral ranges. Glass can also be coated with thin layers of materials like anti-reflective coatings to enhance its optical performance. More recently, advances in photonics and nanotechnology have led to the development of innovative glass types, such as photonic crystal and metamaterial glasses, which exhibit unique light-manipulating properties. It is crucial to note that the optical properties of glass, including its refractive index, can vary depending on its composition and temperature, making it important to consult specific data for particular applications. Overall, glass remains a foundational material in optics, its wide applicability owed to its tunable properties and general robustness.

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