Speaker
Description
Accurate interferometric simulations are essential to understand and optimize the performance of current gravitational wave (GW) detectors, as well as to design next-generation observatories. Simulations play a crucial role in improving detector sensitivity, testing new control strategies and developing advanced noise mitigation techniques. Particularly as the global GW network sensitivity band moves toward lower frequencies and fainter astrophysical signals. Finesse has been a key simulation tool for modeling interferometers in the gravitational wave community for over two decades, supporting detectors like LIGO, Virgo and KAGRA. Finesse3 builds on this foundation as a modern, open-source framework with a Python-based interface, symbolic parameters and intuitive component connections. These features make it easier to create and share realistic models, supporting collaboration and reproducibility across the global GW community. This contribution describes the current status and applications of Finesse3, focusing in particular on the modeling of Advanced Virgo. As part of this effort, updated interferometer models are being developed to closely match experimental measurements and provide deeper insight into optical responses and control dynamics. These models are used to investigate unexplained noise sources by comparing simulated and measured transfer functions or other relevant figures of merit. This approach supports the systematic testing of hypotheses related to optical and mechanical couplings, helping to confirm or rule out possible origins.
Beyond current detectors, Finesse3 plays a central role in design studies for future gravitational-wave facilities such as the Einstein Telescope (ET) and Cosmic Explorer. A growing number of studies
now rely on Finesse3 to simulate complex spatial mode behavior, optical asymmetries, and realistic sensing and actuation chains. In particular, it is being used to investigate potential noise sources in ET,
such as birefringence-induced phase shifts in the silicon test masses, which could impact sensitivity through polarization effects.
Finesse3 is a collaborative project within the gravitational wave community, with core development, testing, training materials, tutorials, examples and documentation primarily carried out at Nikhef,
in the Netherlands. As the ability to model and test complex detector behavior prior to implementation becomes increasingly important, tools like Finesse3 enable faster design cycles, systematic
model validation and shared understanding between modeling and commissioning teams. In the broader context of detector evolution, this strengthens our capacity to face the technological challenges of the coming decades in GW astronomy.
