A team of scientists at the California Institute of Technology (Caltech) has developed a tiny chip that can redirect light at an astonishing speed.
The new device changes the direction of a beam of light in just 74 femtoseconds, or 74 quadrillionths of a second.
To put that into perspective, that is about the amount of time it takes light to travel across the width of a single human hair.
The breakthrough could help improve future technologies that depend on light, including faster internet connections, more powerful computers, advanced sensors, and next-generation communication systems.
Light is already used to carry huge amounts of information through fiber-optic cables because it can travel extremely fast.
However, one of the biggest challenges is controlling where light goes. Scientists need ways to quickly redirect or switch light signals without slowing them down.
Most current technologies control light by changing the electrical properties of a material. For example, liquid crystal displays in projectors and optical chips used in telecommunications work by exciting electrons inside a material.
Those electrons must then return to their normal state before the material can respond again. This process creates a speed limit, usually measured in nanoseconds or picoseconds.
Instead of using electricity, the Caltech researchers took a completely different approach. They used one powerful laser beam, called the “pump,” to briefly change the optical properties of a material.
A second, weaker laser beam, known as the “probe,” then passed through the material and was redirected in a new direction.
The system works because of a physical effect called the optical Kerr effect. This effect allows an intense beam of light to briefly change how light travels through a material.
It changes the motion of electrons inside atoms without pushing them into higher energy states. Because the electrons do not need time to relax afterward, the effect happens almost instantly and disappears just as quickly.
On its own, however, the optical Kerr effect is too weak to produce useful changes.
To solve this problem, the researchers designed an ultra-thin structure called a meta-surface. The meta-surface was made from amorphous silicon and covered with billions of tiny pillars that are each smaller than the wavelength of light.
These tiny structures trap and circulate light for a very short time instead of letting it pass straight through. That brief delay greatly strengthens the tiny change caused by the optical Kerr effect, making it powerful enough to redirect a beam of light.
Using this design, the team successfully steered light by angles of up to 13 degrees in only 74 femtoseconds. The researchers found that the switching speed was limited only by the length of the laser pulse used in the experiment, not by the material itself.
This means the technology could become even faster in the future with improved laser systems.
The researchers believe their new chip could become an important building block for future photonic technologies, where light replaces electricity for processing and transmitting information. Such systems could use less energy while operating at far higher speeds than today’s electronic devices.
The study also opens the door to new areas of optical research, including advanced light-based materials and ultrafast computing concepts that were previously difficult to explore.
While more work is needed before the technology can be used in commercial products, the results demonstrate a promising new way to control light at speeds that were previously out of reach.
