An Australian team has finished specialized coatings for two LIGO beamsplitters after three years of development. The large glass components divide laser light and suppress unwanted reflections in the gravitational-wave instrument. Their manufacture required custom automated equipment and strict contamination control. The intended gains in detector sensitivity is expected to depend on installation and commissioning.
An Australian National University team has completed specialized coatings for two beamsplitters intended for a LIGO upgrade. The development took three years. Each component is a glass disc 45 centimetres across and weighs more than 20 kilograms. The result is a pair of manufactured optics for the gravitational-wave instrument, rather than a new astronomical detection.[1], [2]
LIGO uses laser interferometry to look for minute distance changes associated with gravitational waves from events such as black-hole and neutron-star mergers. One coating divides the laser beam into equal parts. The reverse face has an antireflection coating intended to reduce stray light that could interfere with measurement.[1]
The team controlled coating thickness to within one or two nanometres across nearly half a metre. It developed eight automated systems for cleaning, measuring and handling the optics with little direct contact. Work in a clean room limited contamination during manufacture.[1]
The Australian contribution is coordinated through the OzGrav research collaboration. Steve Madden leads the relevant university optics facility; Robert Ward and Deon Hickey described the precision and new manufacturing approaches required. The completed coatings are intended to support an upgrade. A measured sensitivity increase in an operating detector has not yet been established by this component announcement: the intended gain must be assessed after installation and commissioning.[1]
