Prof. Dr. Andreas Freise
Professor of Experimental Physics
Phone:+44 121 414-3565

University of Birmingham

Homepage of Andreas Freise

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Finesse: The Interferometer Simulation Software

At GEO600 we have created a fast and easy to use interferometer simulation software: Finesse (Frequency domain INterfErometer Simulation SoftwarE). We wanted to design, debug and understand our laser interferometers with a simple but powerful tool. For this we needed to be able to simulate many different user-defined optical setups, so that we can play with and learn more about laser interferometer optics.
Example optical setupVideo showing the transmitted beam shape

Finesse Beispiel einer Simulation mit Finesse: Ein Laserstrahl wird in einen Resonator aus zwei Spiegeln geschickt. Der Strahl passt nicht perfekt zum Resonator, so dass beim Durchstimmen des Resonators verschiedene Modenformen beobachtet werden.

Finesse has been actively developed and improved during several decades, particularly for its application within GEO600 and other gravitational-wave projects. We have kept adding features for modelling more complex and realistic optical systems, such as the Gaussian-mode expansion for describing laser beam distortions. More recently, with the release of Finesse 2.0, we are now able to model the response of suspended optical elements to external forces and to the radiation pressure exerted by the laser fields. We have also implemented a simple but powerful way to model quantum noise in precision interferometry, including the use of squeezed light. These new features allow us to continue to better understand and improve the complex optical interferometers of advanced gravitational-wave observatories and to design completely new optical instruments for the future.

Finesse is freely available on all popular desktop operating systems and is open source under the GNU Public License (GPL). To download and find out more, please visit

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