This detector is essentially a multi-mode resonant-mass GW
antenna working on diff erent overtones (OTs) of its acoustic modes that are sensitive to GWs.
Due to the piezoelectric properties of quartz crystals, the
systems acoustic modes which display sensitivity to
GW strains can be read out via piezoelectric coupling
to capacitive electrodes held at small gaps from the
vibrating body.
A gravitational wave is predicted to stretch space-time in one direction and contract it in the perpendicular direction.
https://arxiv.org/pdf/2102.05859.pdf
A ground-breaking detector that aims to use quartz to capture high-frequency gravitational waves has been built by researchers at the ARC Centre of Excellence for Dark Matter Particle Physics (CDM) and The University of Western Australia. In its first 153 days of operation, two events were detected that could, in principle, be high-frequency gravitational waves, which have not been recorded by scientists before. Such high-frequency gravitational waves may have been created by a primordial black hole or a cloud of dark matter particles.
The results were published this month in the American Physical Society APS Physics journal in an article titled “Rare Events Detected with a Bulk Acoustic Wave High Frequency Gravitational Wave Antenna.” The new detector designed by the research team at the CDM to pick up high-frequency gravitational waves is built around a quartz crystal bulk acoustic wave resonator (BAW).
At the heart of this device is a quartz crystal disk that can vibrate at high frequencies due to acoustic waves traveling through its thickness. These waves then induce electric charge across the device, which can be detected by placing conducting plates on the outer surfaces of the quartz disk. The BAW device was connected to a superconducting quantum interference device, known as SQUID, which acts as an extremely sensitive amplifier for the low voltage signal from the quartz BAW. This assembly was placed in multiple radiation shields to protect it from stray electromagnetic fields and cooled to a low temperature to allow low energy acoustic vibrations of the quartz crystal to be detected as large voltages with the help of the SQUID amplifier.
Many researchers question whether anything has the energy to be a strong gravitational-wave source at such high frequencies—above 10 kilohertz—says Rana Adhikari, an experimental physicist at the California Institute of Technology, who is not involved in the levitated sensor project. But he adds that the hypothetical sources linked to dark matter could prove the exception: “We may be surprised by all of the exotica the universe produces in the ultrasonic gravitational-wave regime.”
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