Laser detectors hunt out black holes

17 Jun 2002

Researchers at the University of Adelaide in Australia are investigating laser-based techniques for identifying dark matter in the universe.

Dark matter emits virtually no electromagnetic radiation so it is very difficult to detect. Astrophysicists believe that it can be studied most easily through the gravitational waves that it produces. However, these waves give very weak forces. On Earth they would be enough to move an object by just 1/10000 the width of a proton.

Laser-based detectors offer one way to study these gravitational waves. The laser is split into two and one beam is bounced back and forth many times between widely spaced mirrors to increase the sensitivity. When the beams are recombined any distortions caused by gravitational waves result in an interference pattern.

This technique requires an almost perfect and very stable laser, operating at 100 Watts. The Australian research, led by Peter Veitch and Murray Hamilton, uses a series of linked laser diodes to power a stable infra-red laser based on a garnet crystal doped with the rare earth neodymium.

Laser-based detectors are also being developed in Stanford University but the researchers there have a different method of producing the high-power laser. The study of gravitational waves requires more than one detector, ideally at least four distributed around the Earth, to determine the origin of any signals and to filter background noise. This will mean the collaboration of researchers in both the northern and southern hemispheres.

Two in a series of linked diode-laser heads. Serving as 'pump' sources, these lasers provide the energy to power another more stable laser.