Until recently, physicists widely believed that it was impossible to compress light below the so-called diffraction limit, except when utilizing metal nanoparticles, which also absorb light. As a result, it seemed to be impossible to compress light strongly in dielectric materials like silicon, which are essential for information technologies and had the significant advantage of not absorbing light. Interestingly, it was theoretically shown that the diffraction limit does not apply to dielectrics back in 2006. However, no one has been able to demonstrate this in the actual world due to the fact that it requires such complex nanotechnology that no one has yet been able to create the required dielectric nanostructures.
A research team has created a device known as a “dielectric nanocavity” that successfully concentrates light in a volume 12 times smaller than the diffraction limit.
“We programmed our knowledge of real photonic nanotechnology and its current limitations into a computer. Then we asked the computer to find a pattern that collects the photons in an unprecedentedly small area – in an optical nanocavity – which we were also able to build in the laboratory.”
Optical nanocavities are structures that have been specially designed to retain light so that it does not travel normally, But is tossed back and forth as if two mirrors were facing each other. The closer the mirrors are to one other, the more intense the light between them gets. For this experiment, the researchers created a bowtie structure, which is particularly effective in squeezing photons together due to its unique shape.
The theory of the diffraction limit describes that light cannot be focused to a volume smaller than half the wavelength in an optical system – for example, this applies to the resolution in microscopes.
However, nanostructures can consist of elements much smaller than the wavelength, which means that the diffraction limit is no longer a fundamental limit. Bowtie structures, in particular, can compress the light into very small volumes limited by the sizes of the bowtie and, thus, the quality of the nanofabrication.
When the light is compressed, it becomes more intense, enhancing interactions between light and materials such as atoms, molecules, and 2D materials.
Dielectric materials are electrically insulating. Glass, rubber, and plastic are examples of dielectric materials, and they contrast with metals, which are electrically conductive.
An example of a dielectric material is silicon, which is often used in electronics but also in photonics.
The nanocavity is made of silicon, the dielectric material on which most advanced modern technology is based.
“We programmed our knowledge of real photonic nanotechnology and its current limitations into a computer. Then we asked the computer to find a pattern that collects the photons in an unprecedentedly small area – in an optical nanocavity – which we were also able to build in the laboratory.”
Optical nanocavities are structures that have been specially designed to retain light so that it does not travel normally but is tossed back and forth as if two mirrors were facing each other. The closer the mirrors are to one other, the more intense the light between them gets. For this experiment, the researchers created a bowtie structure, which is particularly effective in squeezing photons together due to its unique shape.
You must be logged in to post a comment.