A new adaptive optics technology is set to transform gravitational-wave detection, allowing LIGO and future observatories like Cosmic Explorer to reach new heights.
By correcting mirror distortions, this breakthrough will enable extreme laser power levels, helping scientists explore the universe’s earliest moments and refine our understanding of black holes and spacetime.
Expanding the Reach of Gravitational-Wave Observatories
A recent study published in Physical Review Letters presents a breakthrough in optical technology that could significantly enhance the reach of gravitational-wave observatories like LIGO (Laser Interferometer Gravitational-Wave Observatory). Led by Jonathan Richardson of the University of California, Riverside, the research demonstrates how this advancement could not only improve current detection capabilities but also lay the foundation for next-generation observatories.
Since its first detection in 2015, LIGO has revolutionized our ability to observe the universe. Future upgrades to its 4-kilometer detectors, along with the planned construction of the 40-kilometer Cosmic Explorer, aim to extend gravitational-wave detection to the earliest moments in cosmic history—before the first stars even formed. However, achieving this goal requires pushing laser power levels beyond 1 megawatt, far exceeding LIGO’s current capabilities.
The study introduces a new low-noise, high-resolution adaptive optics system designed to overcome this limitation. This technology corrects distortions in LIGO’s massive 40-kilogram mirrors, which occur as laser power increases and heats the system. By enabling extreme laser power levels, this breakthrough could dramatically expand the sensitivity of gravitational-wave detectors, bringing us closer to unlocking the universe’s most distant and elusive signals.
Jonathan Richardson explains what gravitational waves are and how the LIGO (Laser Interferometer Gravitational Wave Observatory) experiment detects these waves.
Richardson, an assistant professor of physics and astronomy, explains the paper’s findings in the following Q&A:
What are gravitational waves?
Gravitational waves are a new way to observe the universe. They are predicted by the equations of general relativity. When massive objects accelerate or collide in the universe, distortions in the fabric of space-time propagate out like ripples in a pond at the speed of light. These distortions are gravitational waves and, like electromagnetic waves, they carry energy and momentum. We now have a lot of information about the extreme astrophysical objects like black holes that create them and about the physics of the underlying nature of spacetime that these waves travel through to reach us.
How does LIGO work?
LIGO is one of the largest pieces of scientific equipment in the world. It consists of two 4-kilometer by 4-kilometer long laser interferometers. One of these interferometers is in inland Washington State; the other is outside Baton Rouge, Louisiana. These sister sites operate in tandem, passively listening to any distortions of spacetime that might happen to propagate through Earth as a gravitational wave.
LIGO so far has seen about 200 events of stellar mass compact objects colliding and merging with each other. The overwhelming majority have been mergers of two black holes, but we’ve also seen mergers of neutron stars. I hope we may one day detect some source that is completely unexpected and unpredicted. If you look at the history of astronomy, every time we’ve developed electromagnetic telescopes that can observe a different wavelength of light than has never been observed before, we see the universe literally in a new light and have almost always discovered new types of objects visible in that wavelength band but not in others. I hope the same is true for gravitational waves.
Tell us about the instrument you’ve developed in your lab that has LIGO applications.
My focus at UCR is on developing new types of laser adaptive optical technology to overcome very fundamental physics limitations to how sensitive we can make detectors like LIGO. Across the majority of gravitational wave signal frequencies we can see from the ground, almost all of them are limited in sensitivity by quantum mechanics, by the quantum properties of the laser light itself that we use in the interferometer to bounce off mirrors. The instrument we’ve developed in my lab is designed to deliver precision optical corrections directly to the main mirrors of the LIGO interferometers. Our instrument is designed to sit just centimeters in front of the reflective surface of these mirrors and project very low noise corrective infrared radiation onto the front surface of the mirror. It is the first prototype for a totally new type of approach that uses non-imaging optical principles, which has never been used in gravitational wave detection before.
What is Cosmic Explorer?
Cosmic Explorer is the U.S. concept for a next-generation gravitational-wave observatory, after LIGO. It will be 10 times the size of LIGO, so that’s 40 by 40-kilometer-long interferometer arms. It will be the largest scientific instrument ever built. At their design sensitivity, these detectors will see the universe at earlier times than when the first stars are believed to have formed, when the universe was about 0.1% of its present 14-billion-year age. We will be able to see a snapshot of the universe at a very early stage in time.
Briefly, what does the research paper discuss?
The paper demonstrates that high-precision optical corrections are essential to expanding our gravitational-wave view of the universe. It lays out the potential implications for the impact we expect our new technology to have in the next generation of LIGO and in the years beyond that. Importantly, the paper shows that this type of technology is necessary and adequate to enable much higher levels of circulating laser power in the LIGO detectors than ever before. We expect this technology, and future versions of it, will be able to achieve more power in the interferometer.
Why is it important to do this research?
This research promises to answer some of the deepest questions in physics and cosmology, such as how fast the universe is expanding and the true nature of black holes. There are two contradicting measures right now of the local expansion rate of the universe, which gravitational waves can potentially resolve. Gravitational waves will also provide exquisitely high precision measurements of the detailed dynamics around the event horizons of black holes, allowing us to make direct tests of classical general relativity and alternative theories.
Reference: “Expanding the Quantum-Limited Gravitational-Wave Detection Horizon” by Liu Tao, Mohak Bhattacharya, Peter Carney, Luis Martin Gutierrez, Luke Johnson, Shane Levin, Cynthia Liang, Xuesi Ma, Michael Padilla, Tyler Rosauer, Aiden Wilkin and Jonathan W. Richardson, 5 February 2025, Physical Review Letters.
DOI: 10.1103/PhysRevLett.134.051401
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8 Comments
Has anyone considered that assorted objects creating gravity waves should be accompanied interference of their assorted gravity waves? In which case we should have interference highs and lows of gravity which then might lead to interesting patterns of collections and absences of matter.
Anyone tried a Youngs Slit experiment on gravity waves?
My understanding of physics is limited, but wouldn’t that require the ability to detect a force carrier?
Gravity waves are something else. “In fluid dynamics, gravity waves are waves in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves.” [Wikipedia]
These gravitational waves are likely carried by gravitons and as force carriers they don’t cause fields at low level (i.e. linear) superposition anymore than photons. So no interesting patterns in gravity but what they themselves cause.
“The gravitational wave background (also GWB and stochastic background) is a random background of gravitational waves permeating the Universe, which is detectable by gravitational-wave experiments, like pulsar timing arrays.[1] The signal may be intrinsically random, like from stochastic processes in the early Universe, or may be produced by an incoherent superposition of a large number of weak independent unresolved gravitational-wave sources, like supermassive black-hole binaries.”
Gravitation is very weak, so no slit experiments (at least not yet).
With all due respect this is not about gravitational waves so much as building new equipment. Just as the newer particle colliders are certainly bigger and better but I would argue progress remains elusive: Where are the gravitational waves (and gravitons)? I count six related articles with this one talking about gravitational waves: where’s the “breakthrough”?
I must admit my bias, which has me looking far beyond solutions in space-time to explain unresolved phenomena like gravity. My own research has found it to be a function of information density.
Fascinating observation, of course in very unscientific form those who have hung their hats on this idea of gravitons and gravitational waves will come up with some completely unfalsifiable idea and those who think and reason for themselves (you seem to be one) will be left to their own conclusions. I wouldn’t rely on anyone who uses the word “graviton” in a favorable way to shed light on your very valid point.
Nice
From my perspective, gravity could be explained as an effect of how matter interacts with the ZPE field. Similar to how mass bends space-time in Einstein’s theory of gravity, I believe that mass might cause distortions in the ZPE field, which is what we experience as gravity. The interesting part is that if we could tune objects to the ZPE field, we might be able to control or even reduce gravity, possibly leading to anti-gravity technology. So, for me, gravity might not just be a force caused by mass but something that can be influenced by how mass interacts with this underlying energy field in space.
From scientist’s perspective there is no other perspective than what can be quantified – yours is just words.