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Microwaveguides Could Speed Control of Light Flux in PICs

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NIZHNY NOVGOROD, Russia, Jan. 2, 2019 — In order to increase the speed with which photonic integrated circuits (PICs) control light flux, researchers are investigating new materials with high optical nonlinearity. Among the promising materials are microwaveguides based on graphene, a material in which charge carrier concentrations can be effectively controlled using optical pumping or applied bias voltage. The work of a team from the Lobachevsky State University of Nizhny Novgorod—National Research University (UNN, also known as Lobachevsky University) could provide a new perspective on the dynamics of waves in nonstationary microwaveguides that could contribute to advances in PICs.

While exploring potential materials for creating PICs, the UNN team developed a theory for the conversion of light waves propagating over the surface of graphene, when the concentration of electrons in graphene changes over time. The interaction of electrons with the light field was precisely taken into account. As a result of their study, the researchers ruled out the possibility of amplifying light waves by changing the concentration of electrons.

Surface Plasmon propagating along a graphene sheet, Lobachevsky University.

(a) Illustration of a surface plasmon propagating along a graphene sheet at t < 0. (b) Time dependence of the graphene carrier density. (c) Dispersion diagram showing the frequency transformation of the initial plasmon when the carrier density decreases from N1 to N2. Courtesy of Lobachevsky University.


The researchers took a general theoretical approach to calculate the graphene plasmon transformation after rapid changes of the Fermi level and carrier density, basing their approach on solving the Maxwell equations supplemented by the microscopic current equation. They derived formulas for the amplitudes of the transmitted and reflected plasmons after a rapid carrier density drop. The relation of these amplitudes and the Fourier transformed finite-difference time-domain (FDTD) fields was established. The results of the analytical and FDTD approaches refuted claims of plasmon amplification under rapid carrier changes that have appeared in recent theoretical studies, the researchers said. The team believes that the theoretical and computational approaches it presents could form a basis of time-varying electromagnetics of graphene plasmonics.

Professor Alexei Maslov said, “Our study is aimed at developing the physical principles of ultrafast photon control in integrated microchips, in other words, at improving the performance of microcircuits and microchips used in microelectronics and nanoelectronics.”

The research was published in Optica, a publication of The Optical Society (https://doi.org/10.1364/OPTICA.5.001508).

Published: January 2019
Glossary
integrated photonics
Integrated photonics is a field of study and technology that involves the integration of optical components, such as lasers, modulators, detectors, and waveguides, on a single chip or substrate. The goal of integrated photonics is to miniaturize and consolidate optical elements in a manner similar to the integration of electronic components on a microchip in traditional integrated circuits. Key aspects of integrated photonics include: Miniaturization: Integrated photonics aims to...
graphene
Graphene is a two-dimensional allotrope of carbon consisting of a single layer of carbon atoms arranged in a hexagonal lattice pattern. It is the basic building block of other carbon-based materials such as graphite, carbon nanotubes, and fullerenes (e.g., buckyballs). Graphene has garnered significant attention due to its remarkable properties, making it one of the most studied materials in the field of nanotechnology. Key properties of graphene include: Two-dimensional structure:...
optoelectronics
Optoelectronics is a branch of electronics that focuses on the study and application of devices and systems that use light and its interactions with different materials. The term "optoelectronics" is a combination of "optics" and "electronics," reflecting the interdisciplinary nature of this field. Optoelectronic devices convert electrical signals into optical signals or vice versa, making them crucial in various technologies. Some key components and applications of optoelectronics include: ...
plasmon
Calculated quantity of the entire longitudinal wave of a solid substance's electron gas.
plasmonics
Plasmonics is a field of science and technology that focuses on the interaction between electromagnetic radiation and free electrons in a metal or semiconductor at the nanoscale. Specifically, plasmonics deals with the collective oscillations of these free electrons, known as surface plasmons, which can confine and manipulate light on the nanometer scale. Surface plasmons are formed when incident photons couple with the conduction electrons at the interface between a metal or semiconductor...
Research & TechnologyeducationLobachevsky UniversityEuropeintegrated photonicsOpticsMaterialsgrapheneoptoelectronicsphotonic integrated circuitsPICsplasmonplasmonicsmicroelectronicsnanoelectronicslight wavesLight Sources

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