In many experiments and technologies, such as atomic force microscopy, detecting these minute positional changes is essential. Weak value amplification has shown that, under specific conditions, even very small modifications in the paths inside an interferometer can translate into a large change at the output, because the device compares overlapping light waves.
LMU physicist Carlotta Versmold and colleagues in the MCQST Cluster of Excellence, working with a team at Tel Aviv University, have now extended this scheme so that it also amplifies changes affecting the incoming beam itself. This extension enables measurements with higher precision than before and opens possibilities for sensing tasks that were previously difficult to achieve.
The researchers illustrate that a laser beam reflected from a distant window can in principle pick up vibrations in the glass produced by speech inside a room. In such a case, the amplified signal at the interferometer output could carry information about the conversations, highlighting the method's potential for remote vibration and sound detection.
In a standard interferometer, any fluctuation in the incoming light usually appears identically in both arms and cancels out in the combined output. In the weak value approach used for internal beam shifts, the light is split into two slightly different paths that are later recombined and then directed to two outputs.
Versmold's team inserted a Dove prism into one arm of the interferometer. The additional reflection introduced by this prism reverses the direction of the shift in that arm relative to the other, so that the two paths experience equal but opposite displacements. When recombined, these opposite shifts translate into an amplified effective displacement at the output.
Using this setup, Versmold measured both tilt and lateral displacement of the incoming beam with a precision on the order of tenths of a microradian and tenths of a micrometer, respectively, which is much smaller than the beam diameter of roughly 2 millimeters. This level of sensitivity shows how subtle geometric changes in the beam path can be resolved.
As a test, she encoded music into the vibrations of a mirror and reflected the laser off that vibrating surface before it entered the interferometer. When the signal was converted back into sound after passing through the interferometer, the audio quality was clearly better than for signals converted from light without using an interferometer.
"This shows the potential of the method for particularly sensitive measurements," says LMU physicist Harald Weinfurter, the study's senior author. The work indicates how quantum-inspired interferometric techniques can enhance classical sensing applications without altering the basic properties of the light source.
Research Report:Interferometric Amplification and Suppression of External Beam Shifts
Related Links
Ludwig-Maximilians-Universitat Munchen
Understanding Time and Space
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
