Zhejiang University, Shanxi University team unleashes sub-nanometer light field potential
A new waveguide scheme reported recently in Advanced Photonics promises to unlock the potential of sub-nanometer light fields; researchers at Zhejiang University and Shanxi University have made a breakthrough in this area.
"Generating a sub-nanometer-confined optical field in a nanoslit waveguiding mode."
In coupled nanowire pairs, light is bound in nanoslit (nanolight).
Traditionally, there are two ways to localize light beyond the typical diffraction limit: dielectric confinement and plasmonic confinement. However, challenges such as precision manufacturing and optical losses prevent limiting the light field to levels below 10 nanometers or even 1 nanometer.
Imagine this: light travels from a regular fiber, through a fiber cone, and finds its destination in a coupled nanowire pair (CNP). In the CNP, the light transforms into extraordinary nanoslit modes, producing confined light fields that can be as small as a mere fraction of a nanometer (about 0.3 nanometers). This new approach has an amazing efficiency of up to 95% and a high peak-to-background ratio (peak-to-background ratio).
The new waveguide scheme extends the waveguide range into the mid-infrared spectral range, further advancing the nanocosmos. Optical confinement (Optical confinement) is now possible down to a staggering scale of about 0.2 nanometers (λ/20000).
Schematic diagram of the CNP waveguide scheme.
Mode evolution in stand-alone CdS CNP waveguides.
Sub-nanometer confined light field of nano-optical modes in the visible spectrum.
On the basis of numerical calculations, the experimental team demonstrated a waveguide scheme that generates sub-nanometer-confined light fields. The potential applications of this breakthrough are stunning. A light field so localized that it can interact with individual molecules or atoms is expected to advance the fields of light-matter interactions, super-resolution nanoscopy, atom/molecule manipulation and ultrasensitive detection.
"Unlike previous methods, the waveguide scheme is itself a linear optical system and thus has many advantages." Prof. Limin Tong of Zhejiang University's Nanophotonics Research Group notes, "It enables broadband and ultrafast pulse operation and allows the combination of multiple sub-nanometer optical fields. The ability to design spatial, spectral and temporal sequences in a single output opens up endless possibilities."
Since the field confinement demonstrated here reaches the same scale as a single small molecule, such fields can provide spatially inhomogeneous and asymmetric light fields with large field gradients at the chemical bond and even atomic scales, thus providing an efficient and flexible platform for exploring light-matter interactions at the single-molecule or atomic level, and for the development of everything from super-resolution nanoscopes and atom/molecule manipulation to ultrasensitive detection in a a wide range of optical technologies.
"We are standing at the precipice of a new age of discovery, with the tiniest areas of existence within our grasp."
Reference link:
[1]https://phys.org/news/2023-07-waveguiding-scheme-enables-highly-confined.html
[2] https://www.spiedigitallibrary.org/journals/advanced-photonics/volume-5/issue-04/046003/Generating-a-sub-nanometer-confined- optical-field-in-a-nanoslit/10.1117/1.AP.5.4.046003.full?SSO=1
