Vortices and surface waves generated in superfluids are used for laboratory-scale analog gravity experiments. Specifically, phonon excitations in supercooled helium generate quantum vortices that are equivalent to the gravitational geometry from a spinning black hole. Non-contact optical methods of these vortices and surface waves are required to measure their unique properties. However, experimental challenges arise from the low optical contrast of liquid helium and micron to nano scale feature sizes of the vortices and surface waves. A modified experimental method is being explored, which was inspired the ancient technology of Chinese magic mirrors ^[1]. These ancient mirrors were prepared with localised stresses which deform their surface on the nano-scale. It is not possible to see these imperfections directly, due to their nano-scale size. However, these predefined imperfections reveal their hidden structure when observing diverging light reflected at relatively large distances. We demonstrate using a similar approach for measuring phonon/vortex activity in thin films of superfluid helium.

References:

[1] Se-yuen Mak and Din-yan Yip 2001 Phys. Educ. 36 102.