Humans experience the world in three dimensions, but a collaboration in
Japan has developed a way to create synthetic dimensions to better
understand the fundamental laws of the universe and possibly apply them to
advanced technologies.
They published their results on January 28, 2022 in Science Advances.
"The concept of dimensionality has become a central fixture in diverse
fields of contemporary physics and technology in past years," said paper
author Toshihiko Baba, professor in the Department of Electrical and
Computer Engineering, Yokohama National University. "While inquiries into
lower-dimensional materials and structures have been fruitful, rapid
advances in topology have uncovered a further abundance of potentially
useful phenomena depending on the dimensionality of the system, even going
beyond the three spatial dimensions available in the world around us."
Topology refers to an extension of geometry that mathematically describes
spaces with properties preserved in continuous distortion, such as the twist
of a mobius strip. When combined with light, according to Baba, these
physical spaces can be directed in a way that allows researchers to induce
highly complicated phenomena.
In the real world, from a line to a square to a cube, each dimension
provides more information, as well requires more knowledge to accurately
describe it. In topological photonics, researchers can create additional
dimensions of a system, allowing for more degrees of freedom and
multifaceted manipulation of properties previously inaccessible.
"Synthetic dimensions have made it possible to exploit higher-dimensional
concepts in lower-dimensional devices with reduced complexity, as well as
driving critical device functionalities such as on-chip optical isolation,"
Baba said.
The researchers fabricated a synthetic dimension on a silicon ring
resonator, using the same approach used to build complementary
metal-oxide-semiconductors (CMOS), a computer chip that can store some
memory. A ring resonator applies guides to control and split light waves
according to specific parameters, such as particular bandwidths.
According to Baba, the silicon ring resonator photonic device acquired a
"comb-like" optical spectra, resulting in coupled modes corresponding to a
one-dimensional model. In other words, the device produced a measurable
property—a synthetic dimension—that allowed the researchers to infer
information about the rest of the system.
While the developed device comprises one ring, more could be stacked to
cascade effects and quickly characterize optical frequency signals.
Critically, Baba said, their platform, even with stacked rings, is much
smaller and compact than previous approaches, which employed optical fibers
connected to various components.
"A more scalable silicon photonic chip platform provides a considerable
advancement, as it allows photonics with synthetic dimensions to benefit
from the mature and sophisticated CMOS commercial fabrication toolbox, while
also creating the means for multi-dimensional topological phenomena to be
introduced into novel device applications," Baba said.
The flexibility of the system, including the ability to reconfigure it as
necessary, complements equivalent static spaces in real space, which could
help researchers bypass the dimensional constraints of real space to
understand phenomena even beyond three dimensions, according to Baba.
"This work shows the possibility that topological and synthetic dimension
photonics can be used practically with a silicon photonics integration
platform," Baba said. "Next, we plan to collect all topological and
synthetic dimension photonic elements to build up a topological integrated
circuit."
Reference:
Armandas Balčytis, Synthetic dimension band structures on a Si CMOS
photonic platform, Science Advances (2022).
DOI: 10.1126/sciadv.abk0468.
Tags:
Physics