1,720,974 research outputs found
Adaptive graphene electronics and plasmonics
No full textGraphene, the world’s first two dimensional material, has attracted great interest in the scientific community due to its unique behaviours such as the dramatic tunability of its electronic and optical properties, strong lightmatter interactions, and high values of carrier mobility which render graphene as a fascinating material for photodetection, plasmonic devices, and modulation of terahertz frequency radiation. To realise the next generation of graphene devices we must find new ways to adaptively control the electronic and optical properties of graphene and other two dimensional materials. In this thesis I propose a method to optically control the electronic properties of graphene in a spatially resolved, non-volatile, yet reversible manner via the use of photorefractive lithium niobate. The method I propose relies on the ability of lithium niobate to sustain optically defined charge distributions which result in large electrostatic fields at the surface of the crystal. By transferring graphene onto lithium niobate crystals I show that the optically defined electrostatic surface charges in the substrate are capable of tuning the DC electrical conductivity of graphene in a behaviour which is non-volatile yet reversible under thermal annealing. Further, I utilise this effect in a plasmonic device consisting of a hybrid graphene-metal metasurface on lithium niobate where the optical tuning effect is capable of altering the transmissive properties of the device at terahertz frequencies. Finally, I show through simulations that by spatially patterning charge distributions it is possible to create optically defined plasmonic devices on graphene on lithium niobate. Such devices would not need permanent lithographic patterning of metasurfaces, yet instead would rely on optically defined regions of high and low conductivity graphene to sustain a plasmonic resonance. If such devices can be experimentally achieved this would allow for rewritable yet non-volatile plasmonic structures in graphene and open the doors to a truly reconfigurable plasmonic platform for two dimensional materials
Dataset for Thesis: Adaptive Graphene Electronics and Plasmonics
No full textThis data supports Doctoral thesis University of Southampton 2020/21. This data contains experimental and simulated investigations of graphene on photoresponsive lithium niobate substrates for tunable electronic and plasmonic applications. The data here is saved in CSV (comma separated value) format, which can be opened with a wide range of freely available software, such as text editors, or spreadsheet readers.</span
Dataset: THz-TDS Parameter Extraction: Empirical Correction Terms for the Analytical Transfer Function Solution
No full textDataset supports: Gorecki, J., & Apostolopoulos, V. (2021). THz-TDS parameter extraction: Empirical correction terms for the analytical transfer function solution. Applied Optics</span
THz-TDS parameter extraction: Empirical correction terms for the analytical transfer function solution
No full textTerahertz time-domain spectroscopy (TDS) is capable of determining both real and imaginary refractive indices of a wide range of material samples; however, converting the TDS data into complex refractive indices typically involves iterative algorithms that are computationally slow, involve complex analysis steps, and can sometimes lead to non-convergence issues. To avoid using iterative algorithms, it is possible to solve the transfer function analytically by assuming the material loss is low; however, this leads to errors in the refractive index values.Here we demonstrate howthe errors created by solving the transfer function analytically are largely predictable, and present a set of empirically derived equations to diminish the error associated with this analytical solution by an impressive two to three orders of magnitude.We propose these empirical correction terms are well suited for use in industrial applications such as process monitoring where analysis speed and accuracy are of the utmost importance.</p
Light controlled conductivity of graphene on photorefractive lithium niobate
No full textWe demonstrate non-volatile control by light of electrical conductivity of graphene deposited on iron doped Lithium Niobate (LN)
Optical gating of graphene
No full textWe demonstrate non-volatile optical tuning of the electronic charge transport properties of graphene by virtue of a photo-responsive iron doped lithium niobate substrate (Fe:LiNbO3)
Engineering high directional sensitivity in non-diffracting metasurfaces
No full textCompact Optical components sensitive to incident wave-vector direction are essential in image-processing, wavefront-manipulation, and metrology such as LIDAR. Here we demonstrate a new class of metasurfaces which exhibit optical spectral features strongly correlated with incident illumination angle. The spectra of such metasurfaces feature sharp transmission dips centred around 800 nm when illuminated at oblique incidence, where the strength of the dip increases as incident angle increases remaining tightly confined within a 100 nm band. The metasurfaces are capable of accepting large incident angles (>30°) without the appearance of higher-order diffraction modes, while displaying dramatic transmission decreases (~80% reduction)
Dataset for Optical Gating of Graphene on Photoconductive Fe:LiNbO3
No full textThis file contains the datatset for "Optical Gating of graphene on Photoconductive Fe:LiNbO3" by J. Gorecki, V. Apostolopoulos, J.Y. Ou, S. Mailis, N. Papasimakis.</span
Data for '3D-Printed Polymer Antiresonant Waveguides for Short Reach Terahertz Applications'
No full textThis is the data for '3D-Printed Polymer Antiresonant Waveguides for Short Reach Terahertz Applications', by L.D. van Putten, J. Gorecki, E. Numkam Fokoua, V. Apostolopoulos and F. Poletti to be published in Applied Optics, 2018.
Data for Figure 5 and Figure 6b&c. Fig3 has all the data to calculate and plot the transmission spectrum in Figure 5. Fig4_1, Fig4_2, Fig4_3 can be used to plot the far fields as seen in figure 4. Z000-Z010 are the beam profiles shown in Fig4b.</span
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