Window Materials Transparency Range
Transmission bands of UV, visible and IR window materials (LiF, MgF₂, CaF₂, fused silica, sapphire, alkali halides, ZnSe, Si, Ge), with the refractive index and the Fresnel-limited transmission 2n/(n² + 1) at any wavelength.
n at 1.55 µm
1.44402
I. H. Malitson, J. Opt. Soc. Am. 55, 1205 (1965)
Reflectance per surface
3.3 %
((n − 1)/(n + 1))², normal incidence
Fresnel-limited transmission
93.6 %
2n/(n² + 1): uncoated, both surfaces, no absorption
Transmission band
0.18–2.2 µm
IR grades transmit to 3 µm.
Fused silica: T_max and n across its bands
Transmission Bands
All materials at 1.55 µm
| Material | Band | n | T_max |
|---|---|---|---|
| 0.12–6 µm | 1.3827 | 95.0 % | |
| 0.12–7 µm | 1.3705 | 95.2 % | |
| 0.13–10 µm | 1.4260 | 94.0 % | |
| 0.15–12 µm | 1.4660 | 93.1 % | |
| 0.17–5.5 µm | 1.7462 | 86.2 % | |
| 0.18–2.2 µm | 1.4440 | 93.6 % | |
| 0.18–3.5 µm, 40–100 µm | 1.5277 | 91.6 % | |
| 0.35–2.5 µm | 1.5007 | 92.3 % | |
| 0.3–2.5 µm, 7–100 µm | 2.3833 | 71.4 % | |
| 0.2–15 µm | 1.5280 | 91.6 % | |
| 0.23–25 µm | 1.5398 | 91.4 % | |
| 0.25–55 µm | 1.7490 | 86.2 % | |
| 0.6–40 µm | 2.4059 | 70.9 % | |
| 0.37–13.5 µm | 2.2717 | 73.7 % | |
| 0.6–21 µm | 2.4556 | 69.9 % | |
| 1.2–15 µm, 30–100 µm | 3.4777 | 53.1 % | |
| 1.8–23 µm | — | opaque |
Model
R = ((n − 1)/(n + 1))², T_max = (1 − R)/(1 + R) = 2n/(n² + 1)
An uncoated window that does not absorb, at normal incidence, with the multiple reflections between its two surfaces added in intensity (no thin-film fringes). Absorption only lowers T, most near the band edges, so T_max is an upper bound inside the band. n comes from each material's published Sellmeier formula (the ordinary index for sapphire, crystal quartz and MgF₂, as for a c-cut window). The bands are the Crystran data-sheet transmission ranges; their edges depend on thickness and grade.
Model and references
Textbook approximation. A standard approximation from the literature (for example paraxial, plane-wave or Gaussian-beam), valid within the range the page states. About the tiers
An uncoated, non-absorbing window at normal incidence, its two surfaces' multiple reflections added in intensity: T = 2n/(n² + 1), an upper bound inside the band. n from published Sellmeier fits (the ordinary ray for uniaxial crystals); the bands are Crystran data-sheet ranges, whose edges depend on thickness and grade.
- Born M., Wolf E. (1999). Principles of Optics, 7th ed. Cambridge University Press. Fresnel formulae at normal incidence.
- Crystran. Handbook of Infrared and Ultraviolet Optical Materials, data sheets: transmission ranges and two-surface reflection losses. crystran.com
- refractiveindex.info database (CC0). Sellmeier data sets, each with its original reference shown on the page.
- Li H. H. (1976). Refractive index of alkali halides and its wavelength and temperature derivatives. J. Phys. Chem. Ref. Data 5, 329. LiF, NaCl, KBr, CsI. doi:10.1063/1.555536
- Dodge M. J. (1984). Refractive properties of magnesium fluoride. Appl. Opt. 23, 1980. doi:10.1364/AO.23.001980
- Malitson I. H. (1965). Interspecimen comparison of the refractive index of fused silica. J. Opt. Soc. Am. 55, 1205. doi:10.1364/JOSA.55.001205
- Rodney W. S., Malitson I. H. (1956). Refraction and dispersion of thallium bromide iodide. J. Opt. Soc. Am. 46, 956. KRS-5. doi:10.1364/JOSA.46.000956