It is believed that light is the essence of life, and in the not-too-distant future, it may also serve as the foundation for personal computing demands. Researchers at the University of Tsukuba recently created a nanocavity to capture certain light energy from a “packet” of light, which could facilitate the development of upcoming all-optical computers.
To transfer internet data, fiber optic cables already reap the benefits of the incredibly rapid speed of light. However, before one can view their favorite streaming show, these signals must first be transformed into electrical impulses in the circuitry of the desktop or smart TV.
Scientists are creating new all-optical computers that can conduct computations with light pulses. Nevertheless, accurately controlling packets of light energy is generally hard, and new technology is required to shape light pulses in a switchable approach.
Scientists from the University of Tsukuba examined a novel metallic waveguide with a tiny nanocavity that is only 100 nm long in a report published last month in Nanophotonics. Only specified wavelengths of light can enter inside the nanocavity since its size is precisely regulated.
As a result, the nanocavity behaves almost like a programmable artificial atom. Also, light waves with the same resonant energy are transferred, while wavelengths with different resonant energies are prevented. The lightwave packet is then reshaped because of this.
The researchers used “surface plasmon polaritons” which are light waves that pass over the metal-air interface. This is accomplished by connecting the motion of the light wave in the atmosphere with that of the electrons in the metal just below it.
You can imagine a surface plasmon polariton as like what happens when a strong wind blows across the ocean. The water waves and airwaves flow in concert.
Atsushi Kubo, Senior Author and Professor, University of Tsukuba
The waveguide was made with a dye that varied its fluorescence qualities in response to the presence of light energy.
The researchers used light chirps that were only 10 femtoseconds long (i.e. 10 quadrillionths of a second) and used time-resolved two-photon fluorescence microscopy to produce a “movie” of the ensuing waves. They discovered that only the spectral component fitting the nanocavity’s resonance energy was able to propagate down the metal surface.
“The ability to selectively reshape waveforms will be key to the development of future optical computers,” Professor Kubo says. The findings of this experiment may potentially aid in the development of other ultrafast optical spectroscopy technologies.
The Nanofabrication Platform of the National Institute for Materials Science (NIMS) and the University of Tsukuba collaborated on this research.
Ichiji, N., et al. (2022) Femtosecond imaging of spatial deformation of surface plasmon polariton wave packet during resonant interaction with nanocavity. Nanophotonics. doi.org/10.1515/nanoph-2021-0740.