Light trapped on curved surfaces: "They took advantage of the fact that light bends, or refracts, when it moves from one medium to another. In their simplest experiment, they shot laser light at the edge of a solid glass sphere. The angle of the beam was chosen so that the light - initially travelling in air - would be bent just enough when it entered the glass that it would keep reflecting off the inside surface of the sphere, and so travel along it. When the light inside the sphere reflected off its inner surface, some was also transmitted through the glass, creating a glowing ring on the outside surface (see image).
The team also constructed an object shaped like two trumpet bells stuck end to end - called a hyperbolic surface. The object was made out of aluminium and then coated with oil. Light sent into the oil layer was confined there, bouncing between the metal and air boundaries. The beam spread out ever more quickly, generating a trumpet-shaped glow"