A team of researchers from the Netherlands and the U.S. has found a new way to concentrate light in an incredibly tiny space—about the size of the light’s own wavelength.
This breakthrough could improve technologies like quantum communication, advanced sensors, and tiny lasers used in photonic chips.
The study was led by scientists from AMOLF, TU Delft, and Cornell University and was published in Science Advances on April 18.
Concentrating light on a very small scale is difficult but essential for many modern technologies.
Traditionally, scientists have used two main methods: one relies on resonance (where light is trapped in a cavity but only at one specific wavelength), and the other uses waveguides that act like funnels, squeezing light into a narrow path.
But both of these approaches have limits—especially when it comes to working across a broad range of light wavelengths.
This new method takes a different approach.
It involves using a special structure called a photonic crystal, made from a thin slab of silicon filled with tiny, regularly spaced holes. These holes prevent light from spreading through the material.
However, when two crystals with mirrored hole patterns are placed next to each other, a special boundary is formed. At this boundary, light can move—but only along that narrow edge.
What makes this setup even more exciting is that the light is “topologically protected.” In simple terms, this means it can travel along the path without being scattered or reflected by small imperfections in the material. That protection comes from the unique design—or topology—of the structure.
Daniel Muis, a Ph.D. student at AMOLF, and his team wondered what would happen if this special light-guiding path suddenly ended at a “wall” that blocks the light completely.
According to theory from Cornell University, the light wouldn’t bounce back immediately, because its usual reflections are suppressed. Instead, it would gather or “pile up” at the wall for a short time, amplifying the light in that tiny space.
To test this, the researchers built the structure on a silicon chip and used a special microscope to scan how light behaved on the chip. What they found matched the prediction perfectly: when the waveguide ended at just the right angle, the light bunched up, forming a concentrated, amplified field.
This method works for multiple wavelengths, not just one, making it very useful for real-world applications. The research opens the door to better control of light in small devices and could also be applied to other types of waves, like sound or even electrons.
The next step? The team hopes to use pulsed lasers to study how long the light keeps accumulating and find ways to make the effect even stronger.
