Since LIGO's groundbreaking detection, in 2015, of gravitational waves produced by a pair of colliding black holes, the observatory, together with its European partner facility Virgo, has detected dozens of similar cosmic rumblings that send ripples through space and time.
In the future, as more and more upgrades are made to the LIGO observatories-one in Hanford, Washington, and the other in Livingston, Louisiana-the facilities are expected to detect increasingly large numbers of these extreme cosmic events. These observations will help solve fundamental mysteries about our universe, such as how black holes form and how the ingredients of our universe are manufactured.
One important factor in increasing the sensitivity of the observatories involves the coatings on the glass mirrors that lie at the heart of the instruments. Each 40-kilogram (88-pound) mirror (there are four in each detector at the two LIGO observatories) is coated with reflective materials that essentially turn the glass into mirrors. The mirrors reflect laser beams that are sensitive to passing gravitational waves.
Generally, the more reflective the mirrors the more sensitive the instrument, but there is a catch: The coatings that make the mirrors reflective also can lead to background noise in the instrument-noise that masks gravitational-wave signals of interest.
Now, a new study by the LIGO team describes a new type of mirror coating made of titanium oxide and germanium oxide and outlines how it can reduce background noise in LIGO's mirrors by a factor of two, thereby increasing the volume of space that LIGO can probe by a factor of eight.
