Output Mode Cleaner
The implementation of an output mode cleaner is another field of international interest.
In a gravitational wave detector the gravitational wave signal is encoded in the interferometer’s output beam. Due to microscopic defects in GEO600’s mirrors there is also light in the output beam that does not carry a gravitational wave signal. This light conceals the signal GEO600 is looking for and therefore has to be removed.
The output mode cleaner that was implemented in 2009 is an arrangement of mirrors, a so-called optical resonator, which only lets that light pass through which carries the gravitational-wave signal. The exact design choice of such a resonator and the best system to control the resonators alignment are an active field of research to which GEO600 has been making important contributions.