Shrinking light: A nanoscale optical breakthrough

Imagine shrinking light down to the size of a tiny water molecule, opening up a world of quantum possibilities. This has been an old dream in the world of light science and technology. Recent advances have brought us closer to achieving this extraordinary feat, as researchers from Zhejiang University have made a breakthrough in limiting light to the subnanometer scale.

Traditionally, there have been two approaches to localizing light beyond its typical diffraction limit: dielectric confinement and plasmonic confinement. However, challenges such as precision fabrication and optical loss have prevented the confinement of the optical field to levels below 10 nanometers (nm) or even 1 nm. But now, a new waveguide scheme is reportedly coming in Advanced Photonics promises to unlock the potential of the field of subnanometer optics.

Picture this: light travels from an ordinary optical fiber, begins a transformative journey through the fiber taper, and finds its destination in a coupled-nanowire-pair (CNP). Inside the CNP, light is transformed into extraordinary nano-slit modes, producing a finite optical field that can be as small as a fraction of a nanometer (about 0.3 nm). With an astounding 95 percent efficiency and high peak-to-background ratio, this new approach offers a whole new world of possibilities.

The new waveguide scheme extends its reach into the mid-infrared spectral range, pushing the boundaries of the nanouniverse even further. Optical confinement can now reach astonishing scales of around 0.2 nm (λ/20000), offering more opportunities for exploration and discovery.

Professor Limin Tong of the Zhejiang University Nanophotonics Group notes, “Unlike previous methods, the waveguide scheme presents itself as a linear optical system, bringing a number of advantages. This enables broadband and ultrafast pulsed operation and enables the combination of multiple sub-nanometer optical fields. The ability to engineer spatial, spectral, and temporal sequences in a single output opens up endless possibilities.”

The potential applications of such a breakthrough are staggering. Highly localized optical fields that can interact with individual molecules or atoms hold promise for advances in light-matter interactions, high-resolution nanoscopy, atom/molecular manipulation, and ultrasensitive detection. We stand on the precipice of a new era of discovery, where the smallest planes of existence are within our grasp.

Check out this video summary with an animated demonstration from the author:

https://players.brightcove.net/689254975001/SyeYVVul4l_default/index.html?videoId=6331129848112

Read the article Open Access Gold by L. Yang, Z. Zhou, et al., “Generating a sub-nanometer-limited optical field in the nanoslit waveguide mode,” Photo continued. 5(4), 046003 (2023), two 10.1117/1.AP.5.4.046003.