Modified Michelson interferometer offers promise for short-range gravity experimentation
Modified Michelson interferometer offers promise for short-range gravity experimentation lead image
To investigate possible violations of the Newtonian gravitational inverse-square law, short-range gravity experiments typically involve measuring minute variations of the twist angle of a torsion pendulum, with test mass separations below the 50-micron length scale. Many of these employ optical autocollimators to enable a measurement uncertainty of a few nanoradians in a typical integration time.
Although alternative methods for measuring pendulum twist using interferometers have been used successfully in complicated systems in the past, LeDesma et al. investigated a
relatively simple alternative for testing short-range gravity via the construction of a highly modified Michelson interferometer.
“We built detectors and software [into the interferometer] that would determine fringes and fringe motion that we could use to track the sinusoidal-like motion of the rotation stage we used to drive our flat mirror,” said author Monty Mola.
The modified Michelson interferometer can measure angular deflections in a flat mirror of less than 10 microradians per interference fringe, and also featured additional interference arms to ensure the parallel reflections off the flat mirror were not diverging from each other.
In their proof of concept, the authors compared the performance of the novel interferometric optical system to existing autocollimator-based methods.
“For certain regions of the measurement frequency band, we were able to reach within a factor of ten of our existing autocollimator in terms of sensitivity,” said author Charles Hoyle.
“While the experiment was not able to match the noise floor of the current short-range gravity system, it gave us important insights on improvements that could be made,” added Mola.
Source: “A modified Michelson interferometer to measure sub-milliradian changes in angle,” by C. K. LeDesma, M.P. Ross, B.E. Daly, C.D. Hoyle, and M.M. Mola, AIP Advances (2022). The article can be accessed at http://doi.org/10.1063/5.0100720 .
