Gravitational waves induce a differential strain between free-falling test masses. The most sensitive instruments to measure this kind of effect are laser interferometers. This chapter introduces the working principles of the different optical configuration that were and will be used in gravitational wave detectors: Michelson interferometer, Fabry-Perot resonant cavity, power and signal recycling techniques. Advanced detectors will feature high power levels, therefore the important issue of radiation pressure effects is addressed. Finally, a brief introduction to the topic of diffraction limited beams and high order transverse electromagnetic modes is included.
© 2014 Springer International Publishing Switzerland. 06 March 2014.