1,720,959 research outputs found
Dataset for the paper 'Making liquid crystals twitch under metamaterial-enhanced terahertz illumination: toward strong optical nonlinearity'
No full textDataset for Optics Express article - Making liquid crystals twitch under metamaterial-enhanced terahertz illumination: toward strong optical nonlinearity
Dataset contains:
2 xlsx files:
ResonancePowerTrack.xlsx - THz-TDS calibration data for the resonance power track plot. This corropsonds to Fig 5 (b) in the paper.
EmitterBiasResults.xlsx - Optical transmission data for the hybrid cell for resonant and non-resonant modes. This corrosponds to Fig 5 (c) and (d)
13 Matlab datafiles:
xxpp_date.mat - THz-TDS data for resonance mode of hybrid cell for different emitter bias
qRef_date.mat - Empty quartz cell reference required for THz-TDS extraction.
Files contain metadata, key sets are the tAxis and sAxis providing the timedomain and signal data
1 Code file
test.m - This MATLAB script will perform windowing and and FFT on the THz-TDS .mat files and plot the THz-TDS data for each emitter bias value on a single plot.
The intention is for this to be run in seperate folders for the resonance and non-resonance data
The resonance data corrosponds to the plot made in Fig. 5 (a).</span
DATASET - Terahertz time-domain spectroscopy for characterisation of photoconductive layers and non-linear soft matter systems
No full textThis dataset supports the thesis entitled: Terahertz time-domain spectroscopy for characterisation of photoconductive layers and non-linear soft matter systems. The data set is split into each main body chapter of the thesis. Any required software will be highlighted in the ReadMe file where appropriate.</span
Dataset supporting an article "All-Optical Switching of Liquid Crystals at Terahertz Frequencies Enabled by Metamaterials".
No full text This dataset is supporting the publication "All-Optical Switching of Liquid Crystals at Terahertz Frequencies Enabled by Metamaterials" by B Beddoes et al, in Optics Express.
This dataset contains modelling data generated for the falloff of the local electric field around the MM edges. The dataset is split into 3 subfolders for following the electric field at 90 degrees, 45 degrees and 0 degrees to LC alignment.
LC alignment in this case is parallel to the straight edges of the MMs. Each sub fold contains the distance from the MM edge "z_#" and the Electric field strength "E_#".
3 MATLAB files which contain the models used to generate the figure 4 plots
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Dataset for the paper 'THz-TDS: extracting complex conductivity of two-dimensional materials via neural networks trained on synthetic and experimental data'
No full textDataset for paper titled: "THz-TDS: extracting complex conductivity of two-dimensional materials via neural networks trained on synthetic and experimental data" Published in Optics Express
Training and validation data used for 4 networks:
- Large synthetically trained network using 2e5 training sets
Comparison networks for different training sets
- Small synthetic network 1600 data sets
- Experimental network 800 data sets
- Hybrid trained network with 1600 datasets (800 experimental sets, 800 synthetic sets)
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Terahertz time-domain spectroscopy for characterisation of photoconductive layers and non-linear soft matter systems
No full textThis thesis explores techniques based on machine learning and hybrid metamaterial-liquid crystal systems to enhance terahertz time-domain spectroscopy (THz-TDS) for the probing of complex optical properties and study of non-linear phenomena. First, the use of artificial neural networks to extract the complex conductivity from THz spectra of large-area graphene monolayers is proposed and demonstrated. By combining synthetic and experimentally acquired data into the network training sets, improved performance is demonstrated on out-of-distribution data when compared to traditional techniques and singularly trained networks. Second, non-linear optical behaviour of nematic liquid crystals integrated with two dimensional metasurfaces is investigated. A robust theoretical framework of all-optical switching induced by the electric field of a conventional low-power oscillator-based THz-TDS system is described. This analysis aims to provide a robust theoretical framework to recent observations of anomalous resonance shifts in liquid crystal-loaded metamaterials when subjected to terahertz illumination. The final part of this thesis describes the first direct experimental evidence of liquid crystal reorientation driven by polarised THz radiation. This effect was observed using a purpose built THz-pump optical-probe setup. The reorientation, facilitated by resonant field amplification of a planar metasurface, demonstrates a path toward strong optical nonlinearity in the terahertz regime and the development of novel all-optical active THz devices
THz-TDS: extracting complex conductivity of two-dimensional materials via neural networks trained on synthetic and experimental data
No full textTerahertz time-domain spectroscopy (TDS) has proved immensely useful for probing 2D materials such as graphene. Unlike in the visible regime, the optical properties at terahertz frequencies are highly dependant on charge carrier mobility and scattering time. However, extracting the material properties from the terahertz waveform is a non-trivial process, which can be prone to producing erroneous results. Artificial neural networks have recently been demonstrated as useful tools to extract complex refractive index from terahertz time domain data. Here, we propose the use of artificial neural networks to interpret terahertz spectra of graphene monolayers to extract the charge carrier mobility and scattering time. We demonstrate improved performance on out-of-distribution data by using a combination of synthetically generated spectra and experimental data during training.</p
All-optical switching of liquid crystals at terahertz frequencies enabled by metamaterials
No full textNematic liquid crystals integrated with metallic resonators (metamaterials) are intriguing hybrid systems, which not only offer added optical functionalities, but also promote strong light-matter interactions. In this report, we show with an analytical model that the electric field generated by a conventional oscillator-based terahertz time domain spectrometer is strong enough to induce partial, all-optical switching of nematic liquid crystals in such hybrid systems. Our analysis provides a robust theoretical footing for the mechanism of all-optical nonlinearity of liquid crystals, which was recently hypothesised to explain an anomalous resonance frequency shift in liquid crystal-loaded terahertz metamaterials. The integration of metallic resonators with nematic liquid crystals offers a robust approach to explore optical nonlinearity within such hybrid material systems in the terahertz range; paves the way towards increased efficiency of existing devices; and broadens the range of applications of liquid crystals in the terahertz frequency range
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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