Micro-fabricated devices for manipulating terahertz radiation

This thesis reports on the design, fabrication and testing of microstructured devices for the manipulation of terahertz radiation. In particular, there is an emphasis on the fabrication and test of diffractive optics type components; including a surface micromachined, multilevel SU-8 based Fresnel lens and a micromilled aluminium Fresnel Zone Plate Reflector (FZPR). For both of these devices, the focal spot is characterized by measuring the electric field intensity and phase as a function of distance along the optical axis. This is carried out using a THz Vector Network Analyzer with associated free space optics. The results are compared directly with Finite Difference Time Domain simulations. A commercial FDTD solver, Lumerical, is used throughout the thesis. FDTD is first introduced for the design of antireflective subwavelength surfaces. These surface structures are bulk micromachined in silicon and their performance experimentally validated using THz Time-Domain Spectroscopy and Durham's THz VNA. A compact THz VNA based S11 measurement configuration is presented which uses the FZPR and a single parabolic mirror. This reflection configuration is used for the characterization of liquid samples (e.g. water and Isopropyl Alcohol mixtures) in microfluidic channels. Two types of channels are presented; one is formed using bulk micromachined silicon whereas the other type uses acetate films to create low cost, disposable devices. The results from the compact measurement configuration are compared with those obtained using a more conventional four parabolic mirror transmission arrangement (as found in THz Time-Domain Spectroscopy systems). Even in the compact configuration, the alignment of the components is found to be a significant factor in determining the measurement performance. Consequently, a six-axis micropositioner (Hexapod), is used to automatically sweep the reflector with the aim of producing a self-aligning system

The Effectiveness of a Training Program Based on Theory of Mind in Developing of Emotional Discrimination among Children with Autism Spectrum Disorder

Weakness in the skill of Emotional Discrimination is one of the obstacles that stand in the way of interaction and social communication of children with autism spectrum disorder, and for its development, it is necessary to prepare a program that helps improve deficiencies and gives good indicators of program performance. This study explored the effectiveness of a training program based on a theory of mind on the development of deficiencies in the skill of emotional discrimination. The study is consistent with previous studies and adds to the limited literature on the experience of developing emotional discrimination in children with autism spectrum disorder. The results could be useful in improving social interaction and supporting children's expression and emotional expression needs, which in turn reduces their social and communication deficits

Near-field probing of optical superchirality with plasmonic circularly polarized luminescence for enhanced bio-detection

Nanophotonic platforms in theory uniquely enable < femtomoles of chiral biological and pharmaceutical molecules to be detected, through the highly localized changes in the chiral asymmetries of the near fields that they induce. However, current chiral nanophotonic based strategies are intrinsically limited because they rely on far field optical measurements that are sensitive to a much larger near field volume, than that influenced by the chiral molecules. Consequently, they depend on detecting small changes in far field optical response restricting detection sensitivities. Here, we exploit an intriguing phenomenon, plasmonic circularly polarized luminescence (PCPL), which is an incisive local probe of near field chirality. This allows the chiral detection of monolayer quantities of a de novo designed peptide, which is not achieved with a far field response. Our work demonstrates that by leveraging the capabilities of nanophotonic platforms with the near field sensitivity of PCPL, optimal biomolecular detection performance can be achieved, opening new avenues for nanometrology

A comparative study of Nanowire-based InP and Planar ITO/InP Photodetectors

Photodetectors are a kind of semiconductor devices that convert incoming light to an electrical signal. Photodetectors have different applications in sensors and fiber optic communication systems, and medical diagnosis etc. In this project  Fourier Transform Infrared (FTIR) Spectroscopy is used to investigate a new version  of photodiodes for near-infrared radiation that is based on self-assembled semiconductor nanowires (NWs) which are grown directly on the substrate without any epi-layer. The spectrally resolved photocurrent (at different applied biases) and IV curves (in darkness and illumination) for different temperatures have been studied, respectively. The thesis work also includes a comparison to a planar photodetector based on Indium Tin Oxide (ITO) deposited directly on an InP substrate.  

The Effectiveness of a Training Program Based on Theory of Mind in Developing of Emotional Discrimination among Children with Autism Spectrum Disorder

Weakness in the skill of Emotional Discrimination is one of the obstacles that stand in the way of interaction and social communication of children with autism spectrum disorder, and for its development, it is necessary to prepare a program that helps improve deficiencies and gives good indicators of program performance. This study explored the effectiveness of a training program based on a theory of mind on the development of deficiencies in the skill of emotional discrimination. The study is consistent with previous studies and adds to the limited literature on the experience of developing emotional discrimination in children with autism spectrum disorder. The results could be useful in improving social interaction and supporting children's expression and emotional expression needs, which in turn reduces their social and communication deficits

Field imaging near to the surface of terahertz reflective optics using a vector network analyzer

A vector network analyzer-based quasi-optical measurement system that is suitable for mapping electric field intensity and phase near to the surface of terahertz reflective optics is presented. The system uses a fixed five parabolic mirror and transmitter/receiver head arrangement that has the benefit of requiring only the sample to be swept during measurement. The system has been tested with a micromilled aluminum zone plate reflector used as an exemplar structure. The measured focal point of the zone plate reflector, at its designed frequency of 1 THz, is shown to correspond well to both finite difference time-domain simulations and analytical theory

Computer Vision, IoT and Data Fusion for Crop Disease Detection Using Machine Learning: A Survey and Ongoing Research

Crop diseases constitute a serious issue in agriculture, affecting both quality and quantity of agriculture production. Disease control has been a research object in many scientific and technologic domains. Technological advances in sensors, data storage, computing resources and artificial intelligence have shown enormous potential to control diseases effectively. A growing body of literature recognizes the importance of using data from different types of sensors and machine learning approaches to build models for detection, prediction, analysis, assessment, etc. However, the increasing number and diversity of research studies requires a literature review for further developments and contributions in this area. This paper reviews state-of-the-art machine learning methods that use different data sources, applied to plant disease detection. It lists traditional and deep learning methods associated with the main data acquisition modalities, namely IoT, ground imaging, unmanned aerial vehicle imaging and satellite imaging. In addition, this study examines the role of data fusion for ongoing research in the context of disease detection. It highlights the advantage of intelligent data fusion techniques, from heterogeneous data sources, to improve plant health status prediction and presents the main challenges facing this field. The study concludes with a discussion of several current issues and research trends

Successive Solvent Extraction, Characterization and Antioxidant Activities of Cardoon Waste (Leaves and Stems) Extracts: Comparative Study

The main interest in the valorization of vegetable wastes is due to the peculiarity of their chemical composition in substances that present important properties. Among these substances, antioxidants could replace those industrially manufactured. In the present study, three solvents of different polarities (hexane, ethanol, and water) were applied for the extraction of phenolic compounds from Cynara cardunculus L. waste using two extraction methods: Soxhlet Extraction (SE) and Ultrasonic-Assisted Extraction (UAE). The obtained extracts were then characterized by Fourier-Transform Infrared (FTIR) spectroscopy and spectrophotometric determination of Total Phenolics (TPC), Total Flavonoids (TFC), and Condensed Tannins (CT). Total Antioxidant Capacity (TAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity of ethanol and water extracts of leaves and stems were also evaluated. High extraction yields were obtained by UAE. Water extracts had high yield regardless of the technique used for leaves and stems, and these extracts showed high TAC of 534.72 ± 3.83 mg AAE/g FM for leaves and 215.70 ± 8.87 mg AAE/g FM (mg of ascorbic acid equivalent per g of FM) for stems, and IC50 of 2077.491 μg/mL for leaves and 1248.185 μg/mL for stems. We explain the latter by the high total phenolic contents (TPCs), which reach 579.375 ± 3.662 mg GAE/g FM (mg of gallic acid equivalents per g of fresh matter) for leaves and 264.906 ± 3.500 mg GAE/g FM for stems. These results confirmed that the leaves and stems of the studied cardoon waste were, indeed, interesting sources of natural antioxidants

Physicochemical Characterization of Cardoon “<i>Cynara cardunculus</i>” Wastes (Leaves and Stems): A Comparative Study

The disposal of vegetable wastes in nature is harmful for marine habitats and biota. These types of waste are frequently used as fuel, generating polluting products, with undesired side effects on the environment. Therefore, it is essential to find better alternatives for the capitalisation of these waste products. Their diversified chemical composition can become a potential resource of high added value raw materials. The knowledge of the physicochemical properties of these wastes is therefore essential. The present work aimed for characterising the physicochemical properties of a plant residue belonging to the Asteraceae Family, collected from a vegetable market in Fez city, Morocco. The vegetal tissues were analysed by Scanning Electron Microscopy coupled with EDX, X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Inductively Coupled Plasma Atomic Emission Spectroscopy, and by Thermogravimetric/Differential thermal analyses. Other additional parameters were also measured, such as moisture, volatile matter, ash, and fixed carbon contents. Acidic and basic surface functions were evaluated by Boehm’s method, and pH points at zero charge were equally calculated. The results revealed a strong congruence between the morphological and structural properties of this plant. These vegetal wastes comprise a homogeneous fibrous and porous aspect both in surface and in profile, with a crystalline structure characteristic of cellulose I. A mass loss of 86.49% for leaves and 87.91% for stems in the temperature range of 100 °C to 700 °C, and pHpzc of 8.39 for leaves and 7.35 for stems were found. This study clarifies the similarities and differences between the chemical composition and morphological structure of these vegetal wastes, paving the way for future value-added applications in appropriate fields