1,721,163 research outputs found
Random access actuation of nanowire grid metamaterial
Full text linkDataset supporting:
Cencillo Abad, Pablo, Ou, Jun-Yu, Plum, Eric, Valente, João and Zheludev, Nikolay (2016) Random access actuation of nanowire grid metamaterial. Nanotechnology, 27, 485206</span
Reconfigurable photonic metamaterials
No full textThis thesis reports on the development of a new class of switchable nanostructured photonic metamaterials, Reconfigurable Photonic Metamaterials (RPMs). Over the last decade, fascinating material properties including negative refraction, optical magnetism, invisibility, asymmetric transmission, perfect lenses and many more were demonstrated in metamaterials. Inspired by pioneering work on micro-electro mechanical metamaterials for the terahertz and microwave spectral regions with feature sizes from millimeters to tens and hundreds microns, I develop reconfigurable photonic metamaterials for the optical spectral range that have sub-micron meta molecules and nanoscale design features.In particular, for the first time I developed: Novel fabrication processes for manufacturing reconfigurable photonic metamaterials based on the platform of elastic silicon nitride membranes using focused ion beam lithography, film deposition, precise alignment, etching and annealing techniques. These fabrication techniques have allowed the manufacturing of a wide range of reconfigurable metamaterials consisting of bi-layer (gold/silicon nitride) or tri-layer (gold/silicon nitride/gold) structured membranes suitable for applications as plasmonic RPMs.Novel RPMs tunable by ambient temperature that operate in the optical and near infrared parts of the spectrum. With such metamaterials exploiting the change in plasmonic response due to differential thermal expansion in bimorph nanostructures I have demonstrated 50% changes in optical transmission at the wavelength of 1735 nm when the temperature is ramped from 76 K to 270 K.Novel RPMs operating in the near-infrared part of the spectrum that can be controlled by electric signals. These types of metamaterials harness electrostatic forces on the nanoscale and offer up to 20 MHz modulation bandwidth. At a threshold level of stimulation these metamaterials exhibit non-volatile switching with up to 250% transmission change. As a part of this research I developed a characterization technique that allows imaging and recording of the electrostatic switching under a scanning electron microscope.Novel optically controlled RPMs exploiting near-field optical forces induced by light and optical heating for reconfiguration. Such metamaterials show a new type of optomechanical nonlinearity leading to intensity-dependent transmission that exceeds the cubic nonlinearity of GaAs by seven orders of magnitude. Using CW diode lasers operating at telecommunication wavelengths of 1.3 µm and 1.55 µm I have demonstrated cross-wavelength optical modulation with amplitude of about 1 % that can be achieved at only about 1 mW of average power of the control beam. I also developed the numerical analysis of thermo-opto-mechanical properties of the structures and calculated eigenmodes and cooling constants of the RPMs under modulated laser irradiation.Overall, the development of reconfigurable photonic metamaterials provides a new and flexible platform for the control of metamaterial properties "on demand". Such metamaterials can find applications in sensors, tunable spectral filters, switches, modulators, programmable transformation optics devices and any other application where tunable optical properties are required
Method for optimising the performance of PML in anchor-loss limited model via COMSOL
No full textPerfectly matched layer has been used for solving anchor-loss limited quality factor in the Micro electromechanical systems. However, setting up a well-behaved perfectly matched layer requires users to change the parameters of a perfectly matched layer to give correct results, while the current existing methods for choosing the right parameters are vague and lack theoretical support. Based on the mathematical theory of perfectly matched layer and simulation results of a beam structure's quality factor, this paper proposes a method for choosing the parameter to optimise the performance of perfectly matched layer in COMSOL. The accuracy of the proposed method is proved by matching the effect of substrate height on beam's quality factor with theory prediction. The author also studies the effect of beam height and beam width on the quality factor of the beam. The results demonstrate that simulated quality factors are in agreement with analytical values when the ratio of height over length is small but will show great divergence when height equals the length. This trend can be observed for the beam width as well. Especially for larger ratio of beam width over beam length, instead of decreasing monotonously as analytical equitation would expect, the simulated quality factor will converge into a stable value of 1700, which matches the result of two-dimensional model for the same beam structure. This means that a three-dimensional model has to be used for estimating the quality factor of a beam structure
Optical addressing of nanomechanical metamaterials with subwavelength resolution
No full textMetamaterials that offer “on-demand” control of individual metamolecules are termed “randomly accessible metamaterials”. They can be useful for manipulating the wavefront of electromagnetic radiation, tailoring of the nearfield, and ultimately for multichannel data processing. Here we demonstrate how light can be used to actuate individual metamaterial elements on demand. Selectivity is achieved by constructing the metamaterial from nanomechanical elements that are designed to have slightly different mechanical resonance frequencies. Actuation is controlled by modulation of the optical control signal at the mechanical resonance frequencies of targeted elements, providing an all-optical route to randomly accessible metamaterials with spatial resolution beyond the diffraction limit
Dataset for Optical addressing of nanomechanical metamaterials with subwavelength resolution
No full textDataset supports:
Ou, J., Plum, E., Zheludev, N. (2018). Optical addressing of nanomechanical metamaterials with subwavelength resolution. Applied Physics Letters.</span
Optimization of metamaterials and metamaterial-microcavity based on deep neural networks
No full textComputational inverse-design and forward prediction approaches provide promising pathways for on-demand nanophotonics. Here, we use a deep-learning method to optimize the design of split-ring metamaterials and metamaterial-microcavities. Once the deep neural network is trained, it can predict the optical response of the split-ring metamaterial in a second which is much faster than conventional simulation methods. The pretrained neural network can also be used for the inverse design of split-ring metamaterials and metamaterial-microcavities. We use this method for the design of the metamaterial-microcavity with the absorptance peak at 1310 nm. Experimental results verified that the deep-learning method is a fast, robust, and accurate method for designing metamaterials with complex nanostructures.</p
Optical magnetic field sensing based on metamaterial nanomechanics
No full textWe demonstrate an optical magnetic field sensor based on a metamaterial-microcavity. Actuation of the microcavity by the magnetic Lorentz force controls its reflectivity. Such sensors promise microscale spatial, sub-millisecond temporal and microtesla magnetic field resolution
Dataset to support the journal article 'Optimization of metamaterials and metamaterial-microcavity based on deep neural networks'
No full textThis dataset contains: Data supporting the figures in the article in Excel format</span
Optomechanical guitar: reconfiguring metamaterials with sub-wavelength spatial resolution
No full textOptomechanical metamaterials, where optical signals actuate unique elements of the nanostructure at their eigenfrequency, can be used to modulate metamaterials with sub-wavelength spatial resolution. We demonstrate the first all-optically addressable metadevice operating in the near infrared
Sensing magnetic field with light and nanomechanics
No full textWe demonstrate an optical magnetic field sensor based on a metamaterial-microcavity. Actuation of the microcavity by the magnetic Lorentz force controls its reflectivity. Such sensors promise microscale spatial, millisecond temporal and microtesla magnetic field resolution
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