Python interface to RefractiveIndex database

The original database
https://github.com/polyanskiy/refractiveindex.info-database

Installation

pip install refractiveindex

The package includes the refractiveindex.info database, so the library needs no network access. The download is about 15 MB. See Database version.

Usage

import numpy as np
from refractiveindex import RefractiveIndexMaterial

# Tabulated nk material
SiO = RefractiveIndexMaterial(shelf='main', book='SiO', page='Hass')

SiO.get_refractive_index(600)
# 1.96553846

SiO.get_extinction_coefficient(600)
# 0.001

SiO.get_epsilon(600)
# (3.8633404437869827+0.003931076923076923j)

# Formula-based material
bk7 = RefractiveIndexMaterial(shelf='specs', book='SCHOTT-optical', page='N-BK7')
bk7.get_refractive_index(589.3)
# 1.5168...

# Array input
wavelengths = np.array([400, 500, 600, 700])
SiO.get_refractive_index(wavelengths)
# array([2.15092857, 1.999, 1.96553846, 1.942])

Units

All methods accept an optional unit= parameter. Default is nm. The following calls are all equivalent:

bk7.get_refractive_index(589.3)                 # nm (default)
bk7.get_refractive_index(5893, unit='A')         # Angstrom
bk7.get_refractive_index(5.893e-7, unit='m')     # meters
bk7.get_refractive_index(0.5893, unit='um')      # µm
bk7.get_refractive_index(16978, unit='cm-1')     # wavenumbers
bk7.get_refractive_index(508.8, unit='THz')      # terahertz
bk7.get_refractive_index(2.108, unit='eV')       # electron volts

The same parameter works for get_extinction_coefficient, get_epsilon, and get_wl_range.

Here $c$ is the speed of light, $h$ is the Plank constant, $e$ is the elementary charge.

Valid wavelength range

Every material exposes the wavelength range over which its data are defined:

# Returns (min, max) in the requested unit
bk7.get_wl_range()            # e.g. (300.0, 2500.0)   nm
bk7.get_wl_range(unit='um')   # e.g. (0.3, 2.5)        µm
bk7.get_wl_range(unit='cm-1') # e.g. (4000.0, 33333.3) cm⁻¹

Result is always returned as (min, max).

Out-of-range behavior

No exception is raised for out-of-range wavelengths, but the returned value is not reliable:

Check get_wl_range() before querying if you are not certain the wavelength is within the measured range:

lo, hi = mat.get_wl_range()
if lo <= wavelength <= hi:
    n = mat.get_refractive_index(wavelength)
else:
    raise ValueError(f"wavelength {wavelength} nm is outside the valid range [{lo}, {hi}] nm")

Notes:

• Here the time dependence is assumed to be $\mathrm{e}^{-\mathrm{i} \omega t}$, so $\mathrm{Im}(\varepsilon) > 0$ is responsible for the losses. For the opposite convention, use exp_type:

  SiO.get_epsilon(600, exp_type="exp(+iwt)")  # (n - ik)^2
  # (3.8633404437869827-0.003931076923076923j)
  

  The default is exp_type="exp(-iwt)". You can also write "exp(iwt)", j instead of i, and ω instead of w, for example "exp(-jωt)".
• If there is a space in the name, write underscore instead, i.e. not page='Rodriguez-de Marcos' but page='Rodriguez-de_Marcos'.
• All 9 dispersion formula types used by the refractiveindex.info database are supported: Sellmeier (1), Sellmeier-2 (2), Polynomial (3), RefractiveIndex.INFO (4), Cauchy (5), Gases (6), Herzberger (7), Retro (8), and Exotic (9).
• The data comes from the database included in the package. See Database version.

How to get material page names

You can find the proper "page" name by hovering your cursor on the link in the Data section

Or you can look up folders in this repository
https://github.com/polyanskiy/refractiveindex.info-database

Similar projects

• PyTMM by Pavel Dmitriev — the original database parsing code this project was based on
• RefractiveIndex.jl — Julia interface to refractiveindex.info database

Database version

The package includes a release of the refractiveindex.info database, so a version of the package always gives the same data. To see which release it includes:

import refractiveindex
refractiveindex.DATABASE_VERSION  # 'v2026-05-24'
refractiveindex.DATABASE_COMMIT   # the upstream commit of this release

A new upstream release comes with a new version of the package:

pip install --upgrade refractiveindex

Use another copy of the database

To use data that is newer than the included release, clone the upstream repository and give its database/ folder as db_path:

git clone https://github.com/polyanskiy/refractiveindex.info-database

SiO2 = RefractiveIndexMaterial(shelf='main', book='SiO2', page='Malitson',
                               db_path='refractiveindex.info-database/database')

Old database folder

Versions before 1.2.0 downloaded the database to ~/.refractiveindex.info-database. Version 1.2.0 and later do not use this folder, so you can delete it.

How to cite

If you use the data in research, cite the refractiveindex.info database, as its author asks:

M. N. Polyanskiy, "Refractiveindex.info database of optical constants," Scientific Data 11, 94 (2024). https://doi.org/10.1038/s41597-023-02898-2

To make your results reproducible, also give the database version, for example "refractiveindex.info database v2026-05-24, used through the refractiveindex Python package 1.2.0".

The database is in the public domain (CC0 1.0). A copy of its licence is in refractiveindex/database/LICENSE.

TODO

1. Include EODG data