Modelling optics and laser interferometers
(Our tools for detection gravitational waves)
We make use of several computer simulations and related tools for designing, analysing and optimising laser interferometers. You can find several of these simulation programs on the Wiki pages of the GEO Simulation Group. On gwoptics.org we provide open source software and other resources related to optical simulations:
A sophisticated simulation package for modelling optics and laser interferometers. Developed for the design of gravitational wave detectors, but easy to use for students with simpler lab-based setups. Get the program, the source and plenty of documentation on our Finesse page! See also SimTools, a collection of Matlab utility functions and scripts to be used with Finesse or other numerical simulations.
We needed a simple, powerful tool allowing non-programmers to quickly develop computer tools. Processing is free, cross-platform, provides quality graphics and exports applications for Windows, OS X, Linux, Android and online applets. See our many online examples and our open source Processing library!
Clear illustrations of optical setups are a key element for communicating the results of numerical models. With the Component Library we provide free vector graphics images of many common laser optics building blocks (use e.g. with Inkscape). See also the animated optical layout of the Einstein Telescope for another example for using SVG vector graphics in gravitational waves research.
Modern gravitational wave detectors are enormous scientific instruments, with laser interferometers at their heart. Light has both particle and wave characteristics. It transfers energy like a particle but propagates like a wave. Interferometry can display the wave-like nature of light. We make use of light waves to measure length between mirrors to an extremely high precision. A passing gravitational wave would change the observed distance between the mirrors and can thus be measured.
They key to the successful design and construction of such a laser interferometer, is to ensure that other disturbances, such as environmental noise or technical noise, do not disturb the interferometer signals. The individual elements that compose the interferometers, including mirrors, beam splitters, lasers, modulators, various polarising optics, photo detectors and so forth, are individually well described by relatively simple, mostly-classical physics. However, a new complexity arises from the special application and combination of these elements which is different from other applications. Thus optical design tasks are based on relatively simple mathematics but due to the complexity of the overall system, numerical simulations have to be used.
More information about the mathematical framework for describing the optical systems can be found in this online review article. Expert readers might be interested in this more the 400 pages long `first chapter' on optics in the so-called Virgo Book of Physics by Jean-Yves Vinet.