Imagine shrinking light down to the size of a tiny water molecule, unlocking a world of quantum possi­bilities. This has been a long-held dream in the realms of light science and technology. Recent advance­ments have brought us closer to achieving this incredible feat, as researchers from Zhejiang University have made groundbreaking progress in confining light to subn­anometer scales. 

Tradi­tionally, there have been two approaches to localize light beyond its typical diffraction limit: dielectric confine­ment and plasmonic confinement. However, challenges such as precision fabri­cation and optical loss have hindered the confinement of optical fields to sub-10 nanometer or even 1-nanometer levels. But now, a new waveguiding scheme promises to unlock the potential of sub­nanometer optical fields.

Imagine light that travels from a regular optical fiber, embarking on a trans­formative journey through a fiber taper, and finding its destination in a coupled-nanowire-pair (CNP). Within the CNP, the light morphs into a remarkable nano-slit mode, generating a confined optical field that can be as tiny as a mere fraction of a nanometer. With an astonishing efficiency of up to 95 percent and a high peak-to-background ratio, this novel approach offers a whole new world of possi­bilities. The new waveguiding scheme extends its reach into the mid-infrared spectral range, pushing the boundaries of the nano-universe even further. Optical confinement can now reach an astonishing scale of approximately 0.2 nanometer, offering even more oppor­tunities for exploration and discovery.

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

The potential appli­cations of such approach are awe-inspiring. An optical field so localized that it can interact with individual molecules or atoms holds promise for advancements in light–matter inter­actions, super-resolution nanoscopy, atom/molecule mani­pulation, and ultra­sensitive detection. We stand at the precipice of a new era of discovery, where the tiniest realms of existence are within our grasp. (Source: SPIE)

Reference: L. Yang et al.: Generating a sub-nanometer-confined optical field in a nanoslit waveguiding mode, Adv. Phot. 5, 046003 (2023); DOI: 10.1117/1.AP.5.4.046003

Link: Nanophotonics Group, Zhejiang University, Hangzhou, China