In many historic glasses, colour is shaped by metal nanoparticles such as gold, silver, and copper, formed during firing and locked into the glass matrix. These particles interact strongly with visible light. Electrons start to move collectively and selectively absorb and scatter certain wavelengths. That’s called plasmon resonance. It’s how a tiny amount of metal can produce rich, stable colour without “paint” in the usual sense.
How the Roman Lycurgus Cup gets its colours
Silver stain is a classic example. During the firing of the glass, silver diffuses into the surface. The small silver particles give the glass a thin yellow layer. And if you want the showpiece, take a look at the Roman Lycurgus Cup. It appears green in reflected light, but shine a light from the back, and it turns stunningly red.
This effect is called dichroism. Tiny particles of gold and silver are mixed into the glass. When light is reflected, these particles scatter mostly green light back to your eyes. When light passes through the glass, they absorb some colours and lets red light through instead. The result is one object, two colours. It all depends on how the light travels. It almost feels like magic.
Why this ancient glass trick matters now
That same principle sits underneath sensors, microscopes, data links, and photonic chips. We’re no longer shaping light only for beauty; we’re shaping it for performance. According to Sahoo, controlling light on the nanoscale is key to detecting faint signals, routing information through chips, and building hardware that can keep up with the demands (and tensions) of a highly networked world.
At the University of Twente, this is not a metaphor but a research agenda. In and around the MESA+ Institute, engineers design materials that guide and control light. The Complex Photonic Systems (COPS) group studies how structure and, in some cases, controlled disorder affect how light propagates through it.
They work on photonic band gap crystals, diffusion of light, and Anderson localisation. Instead of trapping colour in a glass pane, the aim is to shape propagation and emission in complex materials, with a level of control you can’t get from bulk optics.
Controlling light: From nanocavities to chips
On the nanoscale interaction side, Dynamic Nanophotonics (DNP) team works with plasmonic nanocavities. These structures squeeze light into tiny “hotspots”. This makes it possible to detect very small signals, for example, from single molecules. The research helps scientists study biomolecular processes that are normally too faint to observe.
Then there is the chip-level translation. The MESA+ Integrated Photonics program develops photonic chips made from materials such as silicon nitride (SiN) and aluminium oxide (Al₂O₃). and targets applications from communications and sensing to photonics for security. This work is directly connected to the research by Himadri Sahoo. She develops next-generation photonic chips for quantum-secure applications. From medieval windows to nanophotonic chips, the idea is the same: small structures can influence how light behaves.
