(June 24, 2015) Professors
Myung-Ki Kim and Yong-Hee Lee, both of the Physics Department at KAIST, and
their research teams have developed a three dimensional (3D) gap-plasmon
antenna which can focus light into a space a few nanometers wide. Their
research findings were published in the June 10th issue of Nano Letters.
Focusing light into a point-like space is an active research
field with many applications. However, concentrating light into a smaller space
than its wavelength is often hindered by diffraction. To tackle this problem,
many researchers have utilized the plasmonic phenomenon of a metal where light
can be confined to a greater extent by overcoming the diffraction limit.
Many researchers have focused on developing a two
dimensional (2D) plasmon antenna and were able to focus a light under 5
nanometers wide. However, this 2D antenna revealed a challenge: the light
disperses to the opposite end regardless of how small its beam was focused. To
solve this difficulty, a 3D structure had to be employed to maximize the
light's intensity.
Adopting the proximal focused-ion-beam milling technology,
the KAIST research team developed a 3D four nanometer wide gap-plasmon antenna.
By squeezing the photons into a 3D nano space of 4 x 10 x 10 nm3 size, the
researchers were able to increase the intensity of light by 400,000 times
stronger than that of the incident light. Capitalizing on the enhanced
intensity of light within the antenna, they intensified the second-harmonic signal
and verified that the light was focused in the nano gap by scanning
cathodoluminescent images.
The researchers anticipate that this technology will improve
the speed of data transfer and processing up to the level of a terahertz (one
trillion times per second) and to enlarge the storage volume per unit area on
hard disks by 100 times. In addition, high definition images of submolecule
size can be taken with actual light, instead of with an electron microscope,
while improving the semiconductor process to a smaller size of few nanometers.
Professor Kim said, “A simple yet ingenious idea has shifted
the research paradigm from 2D gap-plasmon antennas to 3D antennas. This
technology will see numerous applications including in the field of information
technology, data storage, imaging medical science, and semiconductor
processes.”
The research was sponsored by the National Research
Foundation of Korea.