Speaker
Description
Third-generation gravitational wave detectors, like the Einstein Telescope, aim to improve the sensitivity of the detection band in the low-frequency region. For this, displacement sensors with high sensitivity between 200 mHz and 200 Hz are required for seismic isolation. We demonstrate a heterodyne interferometric displacement sensor that is compact and achieves sub-picometer sensitivity in the mentioned frequency range. By decoupling the interferometric readout and the sensing unit using an optical fibre, we reduce the optical components in the sensing unit to a fibre collimator, a polarising beam splitter and a reference mirror, while no electronics are required in the sensing unit at all. We present measurements from our tabletop sensor setup achieving a sensitivity better than 1 pm/√Hz for almost the entire range between 3 Hz and 600 Hz and better than 30 pm/√Hz down to 100 mHz. In addition, we show how we aim to make our sensor even more compact by replacing our current sensing unit with a single meta-structured glass body. Here, we present, in addition to the operating principle, initial fabrication results.