In a potential breakthrough in the field of photonics, a team of researchers reports they have successfully manipulated light at the sub-wavelength scale.
Previously thought to be impossible, the movement of light at distances sizes smaller than its specific wavelength could lead to an entirely new field of microscopic material manipulation, with additional applications in the fields of DNA programming and nanoscale fabrication.
Breaking the Microscopic Limits of Light
Researchers in a variety of fields employ a device known as optical tweezers. By using a pair of lasers focused down to their smallest sizes, optical tweezers allow for the manipulation of material and objects at extremely small scales. For example, researchers studying DNA are able to use optical tweezers to manipulate single proteins or other biological materials at sizes too small for mechanical tweezers to operate.
Still, even optical tweezers have their limits. Current designs used lenses to focus the twin lasers to the smallest point possible, but the actual size of the light wavelength has limited just how precise even this ultra-precision instrument can be. Now, researchers say they have broken that seemingly unbreakable limit, which may pave the way for a whole new range of microscopic optical applications.
Sub Wavelength Limit Broken
“By its nature, light is indeed very difficult to localise on a smaller length scale than its wavelength,” explains Erika Cortes, one of the study’s authors and a Research Fellow at the University of Southampton’s Quantum, Light and Matter Group, “a critical threshold known as the Abbe limit.”
For decades, that limit has operated as a sort of roadblock to engineering materials, drugs, or other objects at scales smaller than the wavelength of light manipulating them. But now, the researchers from Southampton, together with scientists from the universities of Dortmund and Regensburg in Germany, have successfully demonstrated that a beam of light can not only be confined to a spot that is 50 times smaller than its own wavelength but also “in a first of its kind” the spot can be moved by minuscule amounts at the point where the light is confined.
“Using a sophisticated model and numerical simulation, we have successfully demonstrated a novel approach to localise and dynamically manipulate light at a sub-wavelength scale,” said Cortes, whose team’s study results were published in the journal Optica.
According to that research, the key to confining light below the previous impermeable Abbe diffraction limit was accomplished by “storing a part of the electromagnetic energy in the kinetic energy of electric charges.” This clever adaptation, the researchers wrote, “opened the door to a number of groundbreaking real-world applications, which has contributed to the great success of the field of nanophotonics.”
From Theory to Application
The researchers involved in the photonic breakthrough say that up to this point, their work has been primarily mathematical and theoretical. But once validated in the lab setting, they believe it can be a significant step toward all types of sciences that hope to manipulate light and matter at the sub-wavelength scale.
“We believe our novel approach to actively control confined electromagnetic fields could have high-impact consequences across multiple nanophotonic applications,” said Professor Simone De Liberato, the leader of the Quantum Theory and Technology group in the School of Physics and Astronomy at Southampton.
“Looking to the future, in principle, it could lead to the manipulation of micro and nanometre-sized objects, including biological particles,” De Liberato says, “or perhaps the sizeable enhancement of the sensitivity resolution of microscopic sensors.”