Metamaterial Changes Color of Light

Scientists have long known that meta­materials can mani­pulate electro­magnetic waves such as visible light to make them behave in ways that cannot be found in nature. That has led to break­throughs such as super-high reso­lution imaging. Now, UMass Lowell is part of a research team that is taking the tech­nology of mani­pulating light in a new direction.

This illustration shows two incoming photons being converted into one reflected photon as result of light interaction with the nanowire structure in the metamaterial. The nanowires are about 100 nanometers apart from center to center. (Source: UMass Lowell)

The team, which includes colla­borators from UMass Lowell, King’s College London, Paris Diderot Uni­versity and the Univer­sity of Hartford, has created a new class of meta­material that can be tuned to change the color of light. This tech­nology could someday enable on-chip optical communi­cation in computer processors, leading to smaller, faster, cheaper and more power-efficient computer chips with wider bandwidth and better data storage, among other improve­ments. On-chip optical communi­cation can also create more efficient fiber-optic telecommu­nication networks.

“Today’s computer chips use electrons for computing. Electrons are good because they’re tiny,” said Viktor Podolskiy of the De­part­ment of Physics and Applied Physics, who is the project’s principal inves­tigator. “However, the frequency of electrons is not fast enough. But photons could poten­tially increase the chip’s processing speed.” By converting elec­trical signals into pulses of light, on-chip communi­cation will replace obsolete copper wires found on conven­tional silicon chips, Podolskiy explained. This will enable chip-to-chip optical communi­cation and, ulti­mately, core-to-core communi­cation on the same chip.

“The end result would be the removal of the communi­cation bottle­neck, making parallel computing go so much faster,” he said, adding that the energy of photons deter­mines the color of light. “The vast majority of everyday objects, including mirrors, lenses and optical fibers, can steer or absorb these photons. However, some materials can combine several photons together, resulting in a new photon of higher energy and of different color.”

Podolskiy says enabling the inter­action of photons is key to information processing and optical computing. “Unfor­tunately, this nonlinear process is extremely ineffi­cient and suitable materials for promoting the photon inter­action are very rare.” Podolskiy and the research team have discovered that several materials with poor nonlinear charac­teristics can be combined together, resulting in a new meta­material that exhibits desired state-of-the-art nonlinear properties.

“The enhance­ment comes from the way the meta­material reshapes the flow of photons,” he said. “The work opens a new direction in controlling the nonlinear response of materials and may find appli­cations in on-chip optical circuits, dras­tically improving on-chip communi­cations.” (Source: UMass Lowell)

Reference: B. Wells et al.: Structural second-order nonlinearity in plasmonic metamaterials, Optica 5, 1502 (2018); DOI: 10.1364/OPTICA.5.001502

Link: Dept. of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, USA

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