Author: nanooptomechanics

Photonic metamaterial analogue of a continuous time crystal Nature Physics (2023) 

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Time crystals are an eagerly sought phase of matter with broken time-translation symmetry. Quantum time crystals with discretely broken time-translation symmetry have been demonstrated in trapped ions, atoms and spins whereas continuously broken time-translation symmetry has been observed in an atomic condensate inside an optical cavity. Here we report that a classical metamaterial nanostructure, a two-dimensional array of plasmonic metamolecules supported on flexible nanowires, can be driven to a state possessing all of the key features of a continuous time crystal: continuous coherent illumination by light resonant with the metamolecules’ plasmonic mode triggers a spontaneous phase transition to a superradiant-like state of transmissivity oscillations, resulting from many-body interactions among the metamolecules, characterized by long-range order in space and time. The phenomenon is of interest to the study of dynamic classical many-body states in the strongly correlated regime and applications in all-optical modulation, frequency conversion and timing.

Photonic metamaterial analogue of a continuous time crystal
T. Liu, J. Y. Ou, K. F. MacDonald, and N. I. Zheludev
Nat. Phys. (2023) doi: 10.1038/s41567-023-02023-5 [Press coverage]

Detection of sub-atomic movement in nanostructures Nanoscale Advances(2021) 

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Nanoscale objects move fast and oscillate billions of times per second. Such movements occur naturally in the form of thermal (Brownian) motion while stimulated movements underpin the functionality of nano-mechanical sensors and active nano-(electro/opto) mechanical devices. Here we introduce a methodology for detecting such movements, based on the spectral analysis of secondary electron emission from moving nanostructures, that is sensitive to displace- ments of sub-atomic amplitude. We demonstrate the detection of nanowire Brownian oscillations of ~10 pm amplitude and hyper- spectral mapping of stimulated oscillations of setae on the body of a common flea. The technique opens a range of opportunities for the study of dynamic processes in materials science, nanotechnology and biology.

Detection of sub-atomic movement in nanostructures
T. Liu, J. Y. Ou*, K. F. MacDonald, and N. I. Zheludev
Nanoscale Advances (2021) doi: 10.1039/d0na01068e – pdf

An electromechanically reconfigurable metamaterial operating in the near infrared Nature Nanotechnology (2013)

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The first metamaterial electro-optic modulator for the telecommunications band

Current efforts in metamaterials research focus on attaining dynamic functionalities such as tunability, switching and modulation of electromagnetic waves1. To this end, various approaches have emerged, including embedded varactors2, phase-change media3, 4, the use of liquid crystals5, 6, electrical modulation with graphene7, 8 and superconductors9, and carrier injection or depletion in semiconductor substrates10, 11. However, tuning, switching and modulating metamaterial properties in the visible and near-infrared range remain major technological challenges: indeed, the existing microelectromechanical solutions used for the sub-terahertz12and terahertz13, 14, 15 regimes cannot be shrunk by two to three orders of magnitude to enter the optical spectral range. Here, we develop a new type of metamaterial operating in the optical part of the spectrum that is three orders of magnitude faster than previously reported electrically reconfigurable metamaterials. The metamaterial is actuated by electrostatic forces arising from the application of only a few volts to its nanoscale building blocks—the plasmonic metamolecules—that are supported by pairs of parallel strings cut from a flexible silicon nitride membrane of nanoscale thickness. These strings, of picogram mass, can be driven synchronously to megahertz frequencies to electromechanically reconfigure the metamolecules and dramatically change the transmission and reflection spectra of the metamaterial. The metamaterial’s colossal electro-optical response (on the order of 10−5–10−6 m V−1) allows for either fast continuous tuning of its optical properties (up to 8% optical signal modulation at up to megahertz rates) or high-contrast irreversible switching in a device only 100 nm thick, without the need for external polarizers and analysers.

Ref:

An electromechanically reconfigurable plasmonic metamaterial operating in the near-infrared
J. Y. Ou, E. Plum, J. Zhang, and N. I. Zheludev
Nature Nanotech. 8, 252-255 (2013) doi: 10.1038/NNANO.2013.25

Press coverages

Exotic optics: Metamaterial world
Nature: News Feature, Aug 2013 – link

Electrical signals dictate optical properties
Nanotechnology Now, Mar 2013 – link

Electrical Signals Dictate Optical Properties
Science Daily, Mar 2013 – link

Electrical signals dictate optical properties of metamaterial
Laser Focus World, Mar 2013 – link

Metamaterial with adjustable optical properties
R&D, Mar 2013 – link

Variable-property metamaterial has optical application potential
the ENGINEER, Mar 2013 – link

 

Optomechanical metamaterials with giant nonlinearity Advanced Materials (2016) 

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The first demonstration of light driven optomechanical metamaterials exhibiting giant nonlinearity in the near infrared.

Metamaterial nanostructures actuated by light give rise to a large optical nonlinearity. Plasmonic metamolecules on a flexible support structure cut from a dielectric membrane of nanoscale thickness are rearranged by optical illumination. This changes the optical properties of the strongly coupled plasmonic structure and therefore results in modulation of light with light.

Ref:
Giant nonlinearity of an optically reconfigurable plasmonic metamaterial
J. Y. Ou, E. Plum, J. Zhang, and N. I. Zheludev
Adv. Mater. 28, 729-733 (2016) doi: 10.1002/adma.201504467

Visible range plasmonics in the topological insulator Nature Communications (2014) 

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The development of metamaterials, data processing circuits and sensors for the visible and ultraviolet parts of the spectrum is hampered by the lack of low-loss media supporting plasmonic excitations. This has driven the intense search for plasmonic materials beyond noble metals. Here we show that the semiconductor Bi1.5Sb0.5Te1.8Se1.2, also known as a topological insulator, is also a good plasmonic material in the blue-ultraviolet range, in addition to the already-investigated terahertz frequency range. Metamaterials fabricated from Bi1.5Sb0.5Te1.8Se1.2 show plasmonic resonances from 350 to 550 nm, while surface gratings exhibit cathodoluminescent peaks from 230 to 1,050 nm. The observed plasmonic response is attributed to the combination of bulk charge carriers from interband transitions and surface charge carriers of the topological insulator. The importance of our result is in the identification of new mechanisms of negative permittivity in semiconductors where visible range plasmonics can be directly integrated with electronics.

Ref:
Ultraviolet and visible range plasmonics in the topological insulator Bi1.5Sb0.5Te1.8Se1.2
J. Y. Ou, J. K. So, G. Adamo, A. Sulaev, L. Wang, and N. I. Zheludev
Nat. Commun., 5, 5139 (2014) doi: 10.1038/ncomms6139