We have developed several optical detection schemes for studying the dynamics of free fluid interfaces of both classical and quantum (superfluid helium) fluids. One led to a patent application (in review) for a high speed 3D air-fluid interface sensor with EnShape GmbH (Jena, Germany).
In particular we have used synthetic schlieren imaging with background grids and speckle patterns, optical lever methods and the high-sensitivity interferometric technique of off-axis digital holography. Each technique has its own strengths, whether it be for wide-field high-resolution detection of multiple spatial modes, localised and highly broadband frequency detection or nanometric mode amplitude detection.
We are now developing a heterodyne interferometer that can be used as a localised accelerated probe, enabling investigations into the effect of an observer's reference frame.
