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SNU Professor Namkyoo Park Team Develops lattice Medium to Lead the Light-Driven Computing Era
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2020.09.07
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SNU Professor Namkyoo Park Team Develops lattice Medium to Lead the Light-Driven Computing Era
-New optical medium designed with the application of non-Euclidean hyperbolic plane degree of freedom
-Using the topological characteristics of light allows for easy use due to its stability against error and sensitivity to modulation.
▲ (From left) Professor Namkyoo Park of the SNU Department of Electrical and Computer Engineering, Dr. Sunkyu Yu and Dr. Hyunhee Park
-Using the topological characteristics of light allows for easy use due to its stability against error and sensitivity to modulation.
▲ (From left) Professor Namkyoo Park of the SNU Department of Electrical and Computer Engineering, Dr. Sunkyu Yu and Dr. Hyunhee Park
A source technology for the commercialization of optical and quantum computing, which has been spotlighted as the next-generation technology, has been developed for the first time in the world by domestic researchers.
SNU's College of Engineering (Dean Kookheon Char) announced that a research team led by Professor Namkyoo Park of the Department of Electrical and Computer Engineering has developed a new optical medium design technique that is strong to operating conditions and in the processing of errors but can easily modify optical conditions.
The new optical medium design technique developed by the research team is the application of non-Euclidean characteristics that have recently attracted attention in research subjects such as material science, chemistry, solid physics, and optics with structural freedom that is close to infinity. The research team proposed a method to implement the characteristics of hyperbolic geometry optically on an Euclidean plane, and proved for the first time in the world that new light medium can be obtained by implementing a method that produces an effective magnetic field in the light flowing from that structure.
▲ Figure 1. The lettuce-leaf-like grid structure (left) formed on the hyperbolic surface is projected into a two-dimensional Euclidean area to observe the characteristics of the hyperbolic grid structure (right). The red doughnut diagram is an optical resonator, and the emerald diagram is a wave structure that connects each resonator.
This study is the world's first study to observe the topological characteristics of light in the hyperbolic geometry area, and has the theoretical value of extending 'Hofstadter' butterfly' representing the topological properties of electrons from the optical field to the hyperbolic geometry area.
▲Figure 2. (left) In Euclidean space, Hofstadter's butterfly indicating the optical state along the frequency of magnetic fields and light. (middle and right) 'Hofstadter's butterfly' that is newly defined in different hyperbolic geometry lattice structure. It has high sensitivity to magnetic fields and frequencies, enabling efficient modulation.
It was confirmed that the transmittance of light remains close to 100%, especially when an effective magnetic field was applied to a new optically implemented grid medium, even with disorder or error in the structure. At the same time, it was verified that the error can control the transmission of light very strongly and sensitively depending on the strength of the magnetic field, confirming that high-performance optical signal processing is possible beyond the current performance levels.
▲Figure 3. The transmittance of light when the effective magnetic field is applied to a new "lattice" medium that optically embodies the characteristics of the hyperbolic geometry on the Euclidean plane. The permeability of light remains close to 100%, no matter what error (here described as the radius of the disorderly circle) in the structure.
"In photons composed of the corresponding media, nearly 100% permeability is maintained even if operating conditions and process errors are introduced, and at the same time, these permeability characteristics are very sensitive to the strength of the effective magnetic field, which is its biggest difference from the medium defined in the Euclidean space," said Dr. Sunkyu Yu, the paper's first author, said. "There is the advantage of such error resistance and sensitivity being difficult to obtain at the same time, and its characteristics are applicable to optical switches and transistors that can operate efficiently and reliably, ultimately to light-based computing techniques and quantum computer technologies," he added.
"This study is meaningful in that it is the first study to observe the topological characteristics of light in the hyperbolic geometry area," said Professor Namkyoo Park. "In fact, it can be implemented on an Euclidean plane that is familiar and easily implemented, rather than on a hyperbolic geometry that is almost impossible to implement, and at the same time, there is practical value in that it surpasses the performance of existing devices," he added. "In particular, even though topological characteristics attract attention in quantum computing, they show to be valuable future technology due to the fact that they help overcome difficult limits that we face," he further explained.
"We expect to be able to observe various optical phenomena in different non-Euclidean areas in the future," the research team said.
The research results were published on July 29 as the cover paper for the world-renowned journal Physical Review Letters. SNU Professor Namkyoo Park, Dr. Sunkyu Yu and Dr. Hyunhee Park participated in the study, and were supported by the Global Frontier Project (Wave Energy Extreme Control Research Group) of the Ministry of Science and ICT, the Presidential Post-Doc. Fellowship Project of the Ministry of Education, and the KRF Project of the Ministry of Science and ICT.
[Terminology]
1. Hyperbolic Geometry: A geometry (e.g., a hyperbolic plane) having a negative curvature of a certain value and a non-Euclidical field of geometry that deals with geometry above this structure.
2. Effective Magnetic Field: A term referring to a causal element enabling of the movement of certain particles to be controlled similarly to when a magnetic field is applied to electrons. In this study, a structural/material variable that causes the flow of light to "effectively" resemble the movement of electrons under a magnetic field operates as an effective magnetic field.
3. Topological characteristics: Amount of retention through which its property cannot be changed by continuous deformation, an example of which is a soccer ball and doughnut, having different topological topological properties. Physical phenomena with topological properties can have very strong characteristics against errors.
4. Resonator: An optical element capable of storing the energy of light.
5. Waveguide: An optical element capable of propagating the energy of light.