The software supports both the design and optimization of these extremely precise measurement instruments.
VU professor of Gravitational Wave Physics and Nikhef researcher Andreas Freise developed the first version of Finesse in the late 1990s and led its development through to version 2, which has been used by the LIGO, Virgo, and KAGRA collaborations. Together with Dr. Daniel Brown, he decided several years ago to completely rebuild the software using modern development techniques. While Finesse2 was written in C, Finesse3 has been developed in Python, the current standard in scientific programming. The new package enables researchers to model laser interference within a flexible and user-configurable system of lasers, mirrors, and other optical components. Such models are essential for understanding the minute distance changes caused by gravitational waves and for further refining detector performance.
"We needed a more professional approach to instrument modelling, with fewer ad hoc solutions and improved documentation," says Freise. "Finesse3 provides exactly that, and is also available as open-source software via GitLab."
According to Anna Green, assistant professor at Maastricht University, Nikhef researcher, and scientific co-lead of the project, the new version is not only more modern but also significantly more efficient: "Finesse3 is considerably faster than version 2. This allows us to study more complex and subtle optical effects that are crucial for the next generation of gravitational-wave detectors."
The Nikhef team, including senior scientists, software engineers, PhD candidates, and postdoctoral researchers, has also invested heavily in accessible documentation and training for new users. The open architecture of Finesse3 allows researchers worldwide to contribute new features, for example for crystalline mirrors and extremely high laser powers, as envisioned in plans for the Einstein Telescope. Following the release, Freise and his colleagues are planning a series of international workshops to further introduce the package. "We are quite literally taking it on a world tour," says Freise.