It wasn't really Swiss cheese but it was a material that researchers, who conducted the experiment to validate the theory about photonic calculus, liked to call "Swiss cheese".
“Our device contains a block of dielectric material that has a very specific distribution of air holes,” Engheta says. “Our team likes to call it ‘Swiss cheese.’” The Swiss cheese material is a kind of polystyrene plastic; its intricate shape is carved by a CNC milling machine.
“Controlling the interactions of electromagnetic waves with this Swiss cheese metastructure is the key to solving the equation,” Estakhri says. “Once the system is properly assembled, what you get out of the system is the solution to an integral equation.”
(Image credit: Nader Engheta/University of Pennsylvania)