Refractive index database

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Optical constants of He (Helium)
Cuthbertson and Cuthbertson 1936: n 0.275–0.546 µm

Wavelength: µm

Complex refractive index (n+ik)[ i ]

n   k   LogX   LogY   eV

Derived optical constants

Dispersion formula


Conditions & Spec sheet

n_is_absolute: true
temperature: 0 °C
pressure: 101325 Pa


Standard conditions: 0 °C, 760 torr (101.325 kPa).


1) C. Cuthbertson and M. Cuthbertson. The refraction and dispersion of neon and helium. Proc. R. Soc. London A 135, 40-47 (1936)

2) C. Cuthbertson and M. Cuthbertson. On the refraction and dispersion of neon. Proc. R. Soc. London A 83, 149-151 (1910)

* Ref. 1 doesn't cite gas temperature and pressure. See the earlier publication by the same authors (ref. 2) instead.


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Helium, He

Helium (He) is a noble gas that is colorless, odorless, and tasteless. In the realm of optics, helium is frequently employed as a buffer gas in gas lasers such as helium-neon (He-Ne) and carbon dioxide (CO2) lasers. In He-Ne lasers, helium helps to excite neon atoms, thereby facilitating the laser action, while in CO2 lasers, it assists in the quick dissipation of heat. Additionally, helium's low refractive index, which is close to that of a vacuum, makes it useful in interferometry and other precision measurement techniques. Outside of optics, helium is commonly used in cryogenic environments to achieve extremely low temperatures, which are essential for certain high-precision devices like superconducting magnets used in Magnetic Resonance Imaging (MRI). Despite being one of the most abundant elements in the universe, its applications are quite diverse.

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