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Durham University

Quantum Light and Matter


What is ElecSus?

ElecSus is a cross-platform software package developed over many years by members of the JQC. It calculates, in the weak-probe regime, the Electric Susceptibility of an atomic medium.

ElecSus is designed primarily for quantitatively predicting spectra of thermal vapour cells of Sodium, Potassium, Rubidium or Caesium, and fitting experimental data to theory. This facilitates the design of optical devices such as Faraday filters, optical isolators and circular polarisation filters.

How does it work?

We have written two papers about the features of ElecSus. They are both open-access and can be found here:


Example uses of ElecSus

Since version 2, we now include a graphical interface (GUI) for ease of use. This makes getting up and running producing spectra and fitting to experimental data much easier. A screenshot from the GUI is shown below:

Because ElecSus is fast to run, it can be used to make videos showing the evolution of various parameters. One of our main applications involves the Zeeman effect, which shifts atomic energy levels in an applied magnetic field. The videos below show how the optical transition frequencies (involving both ground and excited states) vary as the field is ramped up.

A video showing the emergence of the hyperfine Paschen-Back regime in a thermal Caesium vapour. The data for this video was produced using ElecSus.

Where can I get ElecSus?

ElecSus is hosted and maintained regularly on GitHub:

ElecSus on Github