Using a glycerine-filled tank as the medium, the researchers then fire femtosecond laser pulses focused at different points in the medium to induce light-scattering microbubbles (via multiphoton absorption). An illumination source then reveals these microbubbles as voxels forming a 3D image in the volume of otherwise transparent glycerin.
The volumetric bubble display, as the researchers describe it in the Optical Society of America (OSA) Optica journal, consists of a light source (the femtosecond laser), a 2D galvanometer mirror combined with a varifocal lens and a LCOS-based light modulator. This optical setup is able to perform 3D beam scanning across the transparent medium to form the voxels in a volume of glycerin which acts as the revealing screen.
Thanks to its high-viscosity, glycerin slows down the movement of the microbubbles, making the voxels stable enough to accurately display volumetric graphics with surround viewing angles. Other benefits of the optically-addressed glycerin-filled display is its simplicity, with no wiring.