This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers from The Australian National University (ANU) have engineered new optical coatings for LIGO, the global collaboration hunting gravitational waves from colliding black holes and neutron stars. The ANU team has spent three years developing and applying advanced coatings to two highly specialized beamsplitters for LIGO (Laser Interferometer Gravitational-Wave Observatory), part of an upgrade that will help scientists detect gravitational waves with greater sensitivity than ever before.
Australia's contribution to LIGO is coordinated through OzGrav, the ARC Center of Excellence for Gravitational Wave Discovery. First predicted by Albert Einstein more than a century ago, gravitational waves—tiny ripples in space-time caused by some of the universe's most powerful events—were directly detected for the first time in 2015, opening a new way of studying the universe. Steve Madden, a professor at the ANU Research School of Physics and director of the Australian National Fabrication Facility (ANFF)'s OptoFab ACT Hub, said these are some of the most exacting and precise coatings ever made.
"We spent three years on very challenging research and development and put our heart and soul into building these optics," Madden said. "We really want to see this Australian contribution produce great results for international science." Robert Ward, a professor and director of ANU's Center for Gravitational Astrophysics, a joint facility between the Research School of Physics and the Research School of Astronomy and Astrophysics, said the project drove precision optics to unprecedented levels. "You need exquisite measurement precision, very tightly controlled processes and extreme coating thickness uniformity to build these components," Ward said.
"We're coating this glass to within a nanometer or two across almost half a meter—a few atoms' difference from one edge to the other." Detecting gravitational waves requires measuring changes in distance around a millionth of a billionth of the width of a human hair, using an extremely pure laser beam as a precision ruler. Any tiny change caused by a passing gravitational wave shows up in the resulting light pattern. Each beamsplitter is a 45-centimeter (18-inch) disk made from some of the purest glass in the world, weighing more than 20 kilograms (44 pounds).
The coating on one side splits the laser beam precisely in half; on the other, an ultralow-reflectivity coating more than 1,000 times more effective than an ordinary eyeglass lens coating minimizes interference and improves detector sensitivity. ANU is one of only two groups worldwide capable of producing these coatings to the exacting standards required for gravitational wave detection. Deon Hickey from ANFF OptoFab ACT said achieving the required precision involved developing entirely new approaches to manufacturing and measurement.
"Every component that goes into this detector is pushed to the absolute limit," Hickey said. "There aren't many machines in the world that can meet the requirements, so we had to build our own equipment and find new ways to solve the problems." The team needed to control coating thicknesses with almost single-atomic-layer accuracy across the entire surface, while also ensuring the optics remained exceptionally clean and free from microscopic defects. To achieve this, the researchers developed eight custom automated systems to clean, measure and handle the delicate components without human contact.
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