Laser Interferometers

A laser interferometer has two arms arranged in the shape of an “L.” Mirrors hang on test masses at each end of both arms, and there is a beam splitter is at the intersection of the two arms. Laser light enters the beam splitter, and the beam splitter sends half of the light down one arm and half down the other arm. The laser light bounces between the mirrors many times before recombining.

Schematic of a laser interferometer detector. Image courtesy of LIGO-Caltech.

When the two light beams recombine, they interfere and form a pattern that depends on the difference between the distances they traveled. Sensors measure the light pattern and turn it into electrical signals.

Gravitational waves change the interference pattern, so researchers look for them by examining changes in the pattern over time. Scientists can then figure out which signals are from local disturbances and which are from gravitational waves by comparing data from interferometers in different parts of the world.

Laser Interferometer Detectors