Scientists have announced a new approach to detecting gravitational waves in the Milli-Hertz frequency range, providing access to astrophysical and cosmological phenomena that are currently undetectable by existing instruments.
Gravitational waves have been observed at high frequencies by ground interferometers such as Rigo and Virgo, and at ultra-low frequencies by pulsar timing arrays.
However, the mid-band area remains a scientific blind spot.
The new detector concept, developed by researchers at the University of Birmingham and the University of Sussex, uses cutting-edge optical cavity and atomic clock technology to detect gravitational waves in the elusive Milli-Hertz frequency band (10-1 Hz).
Optical resonator technology for atomic clocks
This study uses advances in optical atomic technology originally developed for optical atomic clocks to reveal detectors that measure small phase shifts in laser light caused by gravitational waves.
Unlike large interferometers, these detectors are compact and relatively immune to earthquakes and Newton’s noise.
“Using mature techniques in the context of optical atomic clocks allows us to extend the range of gravitational wave detection to a completely new frequency range with equipment that fits the laboratory table,” explained Dr. Bella Grera of the University of Birmingham.
“This opens up the exciting possibility of building a global network of detectors like this and searching for signals that remain hidden for at least 10 years.”
Unlock Milli-Hertz Frequency Band
The Milli-Hertz frequency band, sometimes called “midbands,” is expected to host signals from a variety of astrophysical and cosmological sources, including compact binaries of white dwarfs and black holes mergers.
Ambitious space missions such as LISA are also targeting this frequency band, but are scheduled to be released in the 2030s. The proposed optically rich detectors are now able to begin investigating this area.
Professor Xavier Calmette, co-author of the University of Sussex, commented: “The detector can test astrophysical models of galaxy binary systems, explore the mergers of giant black holes, and even search for probabilistic backgrounds from early universes.
“Using this method will begin investigating these signals and open paths for future space missions.”
Extends gravitational waves to lower frequencies
Future space-based missions such as LISA offer excellent sensitivity, but their operations are still over a decade away. The proposed optical cavity detector provides an immediate and cost-effective means for exploring the Milli-HZ band.
This study suggests that integration of these detectors with existing clock networks will expand gravitational wave detection to even lower frequencies, complementing high-frequency observatory such as LIGO.
Each unit consists of two orthogonal ultrastable optical cavity and an atomic frequency reference, allowing for multi-channel detection of gravitational wave signals.
This configuration not only improves sensitivity, but also allows for discrimination of wave polarization and source direction.
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