Physicists at the University of California, Riverside have developed FROSTI, an innovative adaptive optics system that corrects mirror distortions in LIGO under high laser power. This breakthrough, detailed in Optica, paves the way for more sensitive gravitational-wave observatories. It promises to expand astronomers' view of the cosmos by detecting events 10 times farther away.
Gravitational-wave astronomy took a significant step forward with the introduction of FROSTI, a precision wavefront control system designed for the Laser Interferometer Gravitational-Wave Observatory (LIGO). Led by Jonathan Richardson, an assistant professor of physics and astronomy at the University of California, Riverside, the team published their findings in the journal Optica on December 3, 2025.
LIGO, operational since detecting its first gravitational waves in 2015, uses two 4-km-long laser interferometers in Washington and Louisiana to measure tiny spacetime ripples from events like black hole collisions. Its mirrors, each 34 cm across, 20 cm thick, and weighing 40 kg, must remain nearly motionless to sense distortions smaller than 1/1,000th the diameter of a proton.
High laser powers, exceeding 1 megawatt—nearly five times LIGO's current levels—cause thermal distortions in these mirrors. FROSTI, or FROnt Surface Type Irradiator, addresses this by projecting tailored thermal radiation patterns to reshape the mirror surfaces without adding noise. "At the heart of our innovation is a novel adaptive optics device designed to precisely reshape the surfaces of LIGO's main mirrors under laser powers exceeding 1 megawatt—more than a billion times stronger than a typical laser pointer," Richardson explained.
This technology resolves the challenge of balancing increased laser power with quantum precision. "Increasing laser power tends to destroy the delicate quantum states we rely on to improve signal clarity. Our new technology solves this tension by making sure the optics remain undistorted, even at megawatt power levels," Richardson added.
The prototype was tested on a 40-kg LIGO mirror and is set for integration into the LIGO A# upgrade, serving as a testbed for Cosmic Explorer, which will feature 440-kg mirrors. Richardson noted, "The current prototype is just the beginning. We're already designing new versions capable of correcting even more complex optical distortions. This is the R&D foundation for the next 20 years of gravitational-wave astronomy."
The work, conducted with collaborators from UCR, MIT, and Caltech, was funded by the National Science Foundation. It could enable detection of millions of black hole and neutron star mergers, deepening insights into cosmology and extreme matter.