Optical constants
Refractive index of He (Helium)
Smith et al. 1976: n 0.168–0.288 µm
- Data
- tabulated n
- Range
- 0.168–0.2882 µm
- Points
- 25
- Temperature
- 273.15 K
- Licence
- CC0-1.0
Plot
Click the plot to set the calculator wavelength.
At one wavelength
- Refractive index n
- 1.00004
- Extinction coefficient k
- 0
- Permittivity ε1
- 1.00007
- Permittivity ε2
- 0
- Absorption coefficient α
- 0 cm⁻¹
- Penetration depth δ = λ/(2πk)
- — nm
- Abbe number Vd
- —
- Chromatic dispersion dn/dλ
- -1.90703e-05 µm⁻¹
- Group index ng
- 1.00004
- Group velocity dispersion
- — fs²/mm
- Dispersion parameter D
- — ps/(nm·km)
- Photon energy
- 5.63565 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
# He (Helium): Smith et al. 1976: n 0.168–0.288 µm
he = ls.fetch_refractiveindex("main", "He", "Smith", ref="c5c2f188e848453def5970e347399d653df2ffc2")
print(he.range_nm) # (167.96, 288.24) nm
eps = he.eps([220]) # 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_28fbe6311657/lightsmith"
he = ls.Tabulated.model_validate(json.load(urllib.request.urlopen(url)))
print(he.source) # citation and provenance travel with the dataAny dataset here, as the library's Tabulated material (he/smith-1976).
# ... load he as above, then:
sim = ls.Simulation(
particles=[ls.Particle(shape=ls.Sphere(radius_nm=50), material=he)],
medium_index=1.0,
wavelengths=ls.WavelengthRange(start_nm=168, stop_nm=288, 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
- 273.15 K
- pressure
- 101325
References
- doi:10.1103/physreva.13.1422 Refractivities of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, He,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, CO, and Kr for<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>168</mml:mn><mml:mi>≤</mml:mi><mml:mi>λ</mml:mi><mml:mi>≤</mml:mi><mml:mn>288</mml:mn></mml:math>nm, Physical Review A (1976)
Cite
Peter L. Smith, Martin C. E. Huber and W. H. Parkinson. Refractivities of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, He,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, CO, and Kr for<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>168</mml:mn><mml:mi>≤</mml:mi><mml:mi>λ</mml:mi><mml:mi>≤</mml:mi><mml:mn>288</mml:mn></mml:math>nm. Physical Review A, 13, 1422-1434 (1976), doi:10.1103/physreva.13.1422; Data from the refractiveindex.info database (M. N. Polyanskiy, Sci. Data 11, 94 (2024), doi:10.1038/s41597-023-02898-2)
Data
25 rows as published| λ (µm) | n |
|---|---|
| 0.16796 | 1.00003782 |
| 0.16846 | 1.00003781 |
| 0.16991 | 1.00003774 |
| 0.17016 | 1.00003771 |
| 0.17044 | 1.0000377 |
| 0.17134 | 1.00003766 |
| 0.17226 | 1.00003765 |
| 0.17427 | 1.00003746 |
| 0.17709 | 1.00003745 |
| 0.18475 | 1.00003719 |
| 0.18507 | 1.00003717 |
| 0.19013 | 1.00003705 |
| 0.19832 | 1.00003675 |
| 0.1989 | 1.00003678 |
| 0.20588 | 1.00003663 |
| 0.21248 | 1.00003648 |
| 0.22087 | 1.00003632 |
| 0.22116 | 1.00003631 |
| 0.22174 | 1.00003634 |
| 0.24359 | 1.00003597 |
| 0.25077 | 1.00003589 |
| 0.25169 | 1.00003591 |
| 0.25293 | 1.00003587 |
| 0.26321 | 1.00003574 |
| 0.28824 | 1.00003554 |
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 conditions: 0 °C (273.15 K), 760 torr (101.325 kPa).