The “light trap” setup is shown, consisting of a partially transparent mirror, a thin, weak absorber, two converging lenses and a totally reflecting mirror. Normally, most of the incident light beam would be reflected. However, due to precisely calculated interference effects, the incident light beam interferes with the light beam reflected back between the mirrors, so that the reflected light beam is ultimately completely extinguished. The energy of the light is completely sucked up by the thin and weak absorber. Credit: TU Wien