Science and Engineering

Northwestern University

Andrew Geraci, Vicky Kalogera, Shane Larson
Evanston, IL
June 2019

The kilometer-scale Laser Interferometer Gravitational-Wave Observatory (LIGO) interferometers have just begun to detect gravitational waves (GWs), firmly establishing the nascent field of GW astronomy.  It is paramount to study GW radiation across a wide frequency range, as astronomers have done for visible light and other electromagnetic radiation.  While advanced LIGO has achieved remarkable sensitivity at frequencies ranging from 10s of Hz to a few kHz, no established methods can probe the higher frequency part of the spectrum, where undiscovered GW sources may exist, including primordial black holes and other well-motivated dark matter candidates.  A team of researchers at Northwestern University aims to develop and test a 1-meter prototype of a novel (GW) detector, based on optically-levitated dielectric particles in an optical cavity.  The method could extend the search volume of advanced GW observatories by up to 1000 times in the high frequency (HF) range of 10-300 kHz, using an instrument that is a fraction of their size.  To realize the full sensitivity of the detector, the researchers will need to demonstrate trapping and cooling of non-spherical, i.e., disc-like, particles in high vacuum.  After initial tests, they will conduct a 1-year observing run using two detectors for frequencies > 10 kHz.  The frequency coverage of this instrument complements existing and other proposed GW detectors and promises to enable a new HF-GW map of our universe.

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