Ultra-precise coatings help power the next generation of gravitational wave detectors

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 spent three years developing and applying advanced coatings to two highly specialized beamsplitters for LIGO, part of an upgrade that will help scientists detect gravitational waves with greater sensitivity than ever before. These coatings are precise to a few atoms, with the team coating glass to within a nanometer or two across almost half a meter—almost a few atoms' difference from one edge to the other. The project drove precision optics to unprecedented levels, requiring exquisite measurement precision, very tightly controlled processes, and extreme coating thickness uniformity.

ANU is one of only two groups worldwide capable of producing these coatings to the exacting standards required for gravitational wave detection. The coatings are some of the most exacting and precise ever made, with the team putting their heart and soul into building these optics. The project brought together expertise from across ANU, including the Research School of Physics, the Center for Gravitational Astrophysics, and the ANFF OptoFab ACT node. The work was completed inside the new ANU Research School of Physics Clean Room, where the cleanliness requirements matched those used in advanced semiconductor manufacturing facilities. The upgraded detectors will help researchers pick up more gravitational wave events, including weaker signals from farther away, and study the behavior of some of the universe's most mysterious objects in greater detail.

The research involved developing eight custom automated systems to clean, measure, and handle the delicate components without human contact. 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. The project involved challenging research and development, with the team overcoming many technical hurdles to achieve the required precision. The coatings are crucial for the next generation of gravitational wave detectors, enabling scientists to detect weaker signals and study the universe more deeply.

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