Optical constants
Refractive index of Air
Birch and Downs 1994: n 0.350–0.650 µm
- Data
- tabulated n
- Range
- 0.35–0.65 µm
- Points
- 31
- Temperature
- 288.15 K
- Licence
- CC0-1.0
Plot
Click the plot to set the calculator wavelength.
At one wavelength
- Refractive index n
- 1.00028
- Extinction coefficient k
- 0
- Permittivity ε1
- 1.00055
- Permittivity ε2
- 0
- Absorption coefficient α
- 0 cm⁻¹
- Penetration depth δ = λ/(2πk)
- — nm
- Abbe number Vd
- —
- Chromatic dispersion dn/dλ
- -1.61220e-05 µm⁻¹
- Group index ng
- 1.00029
- Group velocity dispersion
- — fs²/mm
- Dispersion parameter D
- — ps/(nm·km)
- Photon energy
- 2.11001 eV
ε = (n + ik)², α = 4πk/λ, ng = n − λ dn/dλ, GVD = λ³/(2πc²) d²n/dλ², D = −(λ/c) d²n/dλ². Group-velocity dispersion is given for formula data only.
Use it in Lightsmith
Load this data in Python, simulate in one more line
pip install lightsmith
import lightsmith as ls
# Air: Birch and Downs 1994: n 0.350–0.650 µm
air = ls.fetch_refractiveindex("other", "air", "Birch", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(air.range_nm) # (350, 650) nm
eps = air.eps([633]) # complex permittivityDownloads the original record once (pinned to the imported snapshot) and caches it.
import json, urllib.request
import lightsmith as ls
url = "https://materials.lightsmith.dev/v1/datasets/ds_7a783385a519/lightsmith"
air = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(air.source) # citation and provenance travel with the dataAny dataset here, as the library's Tabulated material (air/birch-downs-1994).
# ... load air as above, then:
sim = ls.Simulation(
particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=air)],
medium_index=1.0,
wavelengths=ls.WavelengthRange(start_nm=400, stop_nm=650, num=81),
)
res = ls.solve(sim) # exact Mie for a sphere
print(res.q_ext) # extinction efficiency at each wavelengthSame spec runs with DDA, FDTD, BEM or T-matrix: ls.compare(sim, ["mie", "dda"]).
Lightsmith is open source (MIT): Mie, T-matrix, BEM, DDA, FDTD, RCWA, TMM, mode solvers and inverse design behind one spec, on CPU or GPU. GitHub.
Comments and conditions
Conditions
- temperature
- 288.15 K
- pressure
- 101325
References
[Calculation script (Python) - can be used to calculate the refractive index of air for specific values of humidity, temperature, and pressure]
- doi:10.1088/0026-1394/31/4/006 Correction to the Updated Edlén Equation for the Refractive Index of Air, Metrologia (1994)
Cite
K P Birch and M J Downs. Correction to the Updated Edlén Equation for the Refractive Index of Air. Metrologia, 31, 315-316 (1994), doi:10.1088/0026-1394/31/4/006; [Calculation script (Python) - can be used to calculate the refractive index of air for specific values of humidity, temperature, and pressure]; Data from the refractiveindex.info database (M. N. Polyanskiy, Sci. Data 11, 94 (2024), doi:10.1038/s41597-023-02898-2)
Data
31 rows as published| λ (µm) | n |
|---|---|
| 0.35 | 1.000286117508 |
| 0.36 | 1.000285320614 |
| 0.37 | 1.000284593971 |
| 0.38 | 1.000283929371 |
| 0.39 | 1.000283319792 |
| 0.4 | 1.000282759203 |
| 0.41 | 1.00028224239 |
| 0.42 | 1.000281764829 |
| 0.43 | 1.000281322576 |
| 0.44 | 1.000280912177 |
| 0.45 | 1.000280530598 |
| 0.46 | 1.000280175162 |
| 0.47 | 1.000279843501 |
| 0.48 | 1.000279533513 |
| 0.49 | 1.000279243325 |
| 0.5 | 1.000278971266 |
| 0.51 | 1.000278715838 |
| 0.52 | 1.000278475698 |
| 0.53 | 1.000278249637 |
| 0.54 | 1.000278036564 |
| 0.55 | 1.000277835492 |
| 0.56 | 1.000277645529 |
| 0.57 | 1.000277465862 |
| 0.58 | 1.000277295756 |
| 0.59 | 1.000277134536 |
| 0.6 | 1.00027698159 |
| 0.61 | 1.000276836357 |
| 0.62 | 1.000276698322 |
| 0.63 | 1.000276567014 |
| 0.64 | 1.000276441999 |
| 0.65 | 1.00027632288 |
Optical transmission calculator
Free-standing sample in vacuum, normal incidence- Transmittance T
- —
- Reflectance R
- —
Fresnel reflection calculator
- Rp
- —
- Rs
- —
- R = (Rp+Rs)/2
- —
- Phase φp
- —
- Phase φs
- —
- Brewster angle θB
- —
- Critical angle θC
- —
Standard air: dry air at 15 °C, 101.325 kPa and with 450 ppm CO2 content.