Gravitational waves have long been predicted by Albert Einstein using the theory of general relativity, but so far have not been directly observed. Currently, an international array of first-generation, kilometer-scale laser interferometric gravitational-wave detectors, targeted at gravitational-waves in the acoustic band from 10 Hz to 10 kHz, is going into operation. These first-generation detectors are all Michelson interferometers with suspended mirrors. Second-generation detectors are planned, and at the same time, third-generation detectors already come to the fore. In such interferometers new technologies will be applied, involving squeezed light, quantum-non-demolition position sensing and cryogenic cooling of 100 kg super mirrors.