A Microring Resonator Based Negative Permeability Metamaterial Sensor

Metamaterials are artificial multifunctional materials that acquire their material properties from their structure, rather than inheriting them directly from the materials they are composed of, and they may provide novel tools to significantly enhance the sensitivity and resolution of sensors. In this paper, we derive the dispersion relation of a cylindrical dielectric waveguide loaded on a negative permeability metamaterial (NPM) layer, and compute the resonant frequencies and electric field distribution of the corresponding Whispering-Gallery-Modes (WGMs). The theoretical resonant frequency and electric field distribution results are in good agreement with the full wave simulation results. We show that the NPM sensor based on a microring resonator possesses higher sensitivity than the traditional microring sensor since with the evanescent wave amplification and the increase of NPM layer thickness, the sensitivity will be greatly increased. This may open a door for designing sensors with specified sensitivity

Two-dimensional alignment and displacement sensor based on movable broadside-coupled split ring resonators

This paper proposes a two-dimensional alignment and displacement sensor based on movable broadside-coupled split ring resonators (BC-SRRs). As a basis for this sensor, a one-dimensional displacement sensor based on a microstrip line loaded with BC-SRRs is presented firstly. It is shown that compared to previously published displacement sensors, based on SRR-loaded coplanar waveguides, the proposed one-dimensional sensor benefits from a much wider dynamic range. Secondly, it is shown that with modifications in the geometry of the BC-SRRs, the proposed one-dimensional sensor can be modified and extended by adding a second element to create a high-dynamic range two-dimensional displacement sensor. Since the proposed sensors operate based on a split in the resonance frequency, rather than the resonance depth, they benefit from a high immunity to environmental noise. Furthermore, since the sensors' principle of operation is based on the deviation from symmetry, they are more robust to ambient conditions such as changes in the temperature, and thus they can be used as alignment sensors as well. A prototype of the proposed two-dimensional sensor is fabricated and the concept and simulation results are validated through experiment

Radio-Frequency Sensors for High Performance Liquid Chromatography Applications

As a fast-developing analytical technique for separation, purification, identification and quantification of components in a mixture, high performance liquid chromatography (HPLC) has been widely used in various fields including biology, food, environment, pharmacy and so on. As a critical part in the HPLC system, the detector with the feature of high sensitivity, universal detection and gradient-elution compatibility is highly desired. In this dissertation, two types of radio-frequency (RF) sensors for HPLC gradient applications are presented: a tunable interferometer (TIM) and a modified square ring loaded resonator (SRLR). For the TIM-based sensor, the sensitivity is evaluated by measuring a few common chemicals in DI water at multiple frequencies from 0.98 GHz to 7.09 GHz. Less than 84 ppm limit of detection (LOD) is demonstrated. An algorithm is provided and used to obtain sample dielectric permittivity at each frequency point. When connected to a commercial HPLC system and injected with a 10 μL aliquot of 10000 ppm caffeine DI-water solution, the sensor yields a signal-to-noise ratio (SNR) up to 10 under isocratic and gradient elution operations. Furthermore, the sensor demonstrates a capability to quantify co-eluted vitamin E succinate (VES) and vitamin D3 (VD3). For the SRLR-based sensor, where a transmission line and a ring are electrically shorted with a center gap, the detection linearity is characterized by measuring water-caffeine samples from 0.77 ppm to 1000 ppm when connected to the HPLC system. A 0.231 ppm limit of detection (LOD) is achieved, revealing a comparable sensitivity with commercial ultraviolet (UV) detectors. The compatibility of the proposed sensor to gradient elution is also demonstrated. Besides, this work presents a method for the measurement of liquid permittivity without using liquid reference materials or calibration standards. The method uses a single transmission line and a single microfluidic channel which intercepts the line twice. As a result, two transmission line segments are formed with channel sections to measure liquid samples. By choosing a 2:1 ratio for the two line segment lengths, closed-form formulas are provided to calculate line propagation constants directly from measured S-parameters. Then, sample permittivity values are obtained. A coplanar waveguide is built and tested with de-ionized water, methanol, ethanol and 2-propanol from 0.1 GHz to 9 GHz. The obtained performance agrees with simulation results. The obtained sample permittivity values agree with commonly accepted values. Radiofrequency (RF) non-thermal (NT) bio-effects have been a subject of debate and attracted significant interests due to the potential health risks or beneficial applications. A miniature transverse electro-magnetic (TEM) device is designed for broadband investigation of RF NT effects on Saccharomyces cerevisiae growth, a common yeast species. The frequency-dependent yeast permittivity, obtained by measuring the difference between the medium and yeast in the medium, was used to select the applied RF frequencies, i.e., 1.0 MHz, 3.162 MHz, 10 MHz and 905 MHz. The results showed that the RF field at 3.162 MHz reduced yeast growth rates by 11.7%; however, the RF fields at 1.0 MHz and 10 MHz enhanced cell growth rates by 16.2% and 4.3%, respectively. In contrast, the RF field at 905 MHz had no effect on the growth rates

Anomalies in Light Scattering

Scattering of electromagnetic waves lies at the heart of most experimental techniques over nearly the entire electromagnetic spectrum, ranging from radio waves to optics and X-rays. Hence, deep insight into the basics of scattering theory and understanding the peculiar features of electromagnetic scattering is necessary for the correct interpretation of experimental data and an understanding of the underlying physics. Recently, a broad spectrum of exceptional scattering phenomena attainable in suitably engineered structures has been predicted and demonstrated. Examples include bound states in the continuum, exceptional points in PT-symmetrical non-Hermitian systems, coherent perfect absorption, virtual perfect absorption, nontrivial lasing, non-radiating sources, and others. In this paper, we establish a unified description of such exotic scattering phenomena and show that the origin of all these effects can be traced back to the properties of poles and zeros of the underlying scattering matrix. We provide insights on how managing these special points in the complex frequency plane provides a powerful approach to tailor unusual scattering regimes

PT symmetry and exceptional points in metamaterials

Parity-Time (PT) symmetry has recently received much attention as a promising alternative to the condition of Hermiticity. PT symmetric systems have two distinct phases where behaviour is split between Hermitian evolution where it has real eigenvalues and non-Hermitian evolution where it has complex eigenvalues. At the crossover between these two phases, there is an exceptional point: a special kind of eigenvalue degeneracy unique to non-Hermitian system which can result in interesting properties. In this thesis, we will first review the field of metamaterials and show how they can be used to design electromagnetic potentials. We will also review the current understanding of PT symmetry and its associated effects in electromagnetism. We will then develop a new form of parity operator which can be used in conjunction with the time-reversal operator to derive new conditions on the constitutive matrix. This parity operator will then be used to understand the link between PT symmetry and exceptional points with experimental support from a metamaterial system. We will additionally look at some other applications of PT symmetry, specifically in the context of lasing and absorption, and attempt to design a structure which uses this symmetry

Photonic Applications Based on Bimodal Interferometry in Periodic Integrated Waveguides

Tesis por compendio[ES] La fotónica de silicio es una tecnología emergente clave en redes de comunicación e interconexiones de centros de datos de nueva generación, entre otros. Su éxito se basa en la utilización de plataformas compatibles con la tecnología CMOS para la integración de circuitos ópticos en dispositivos pequeños para una producción a gran escala a bajo coste. Dentro de este campo, los interferómetros integrados juegan un papel crucial en el desarrollo de diversas aplicaciones fotónicas en un chip como sensores biológicos, moduladores electro-ópticos, conmutadores totalmente ópticos, circuitos programables o sistemas LiDAR, entre otros. Sin embargo, es bien sabido que la interferometría óptica suele requerir caminos de interacción muy largos, lo que dificulta su integración en espacios muy compactos. Para mitigar algunas de estas limitaciones de tamaño, surgieron varios enfoques, incluyendo materiales sofisticados o estructuras más complejas, que, en principio, redujeron el área de diseño pero a expensas de aumentar los pasos del proceso de fabricación y el coste. Esta tesis tiene como objetivo proporcionar soluciones generales al problema de tamaño típico de los interferómetros ópticos integrados, con el fin de permitir la integración densa de dispositivos basados en silicio. Para ello, aunamos los beneficios tanto de las guías de onda bimodales como de las estructuras periódicas, en términos de la mejora del rendimiento y la posibilidad para diseñar interferómetros monocanal en áreas muy reducidas. Más específicamente, investigamos los efectos dispersivos que aparecen en estructuras menores a la longitud de onda y en las de cristal fotónico, para su implementación en diferentes configuraciones interferométricas bimodales. Además, demostramos varias aplicaciones potenciales como sensores, moduladores y conmutadores en tamaños ultra compactos de unas pocas micras cuadradas. En general, esta tesis propone un nuevo concepto de interferómetro integrado que aborda los requisitos de tamaño de la fotónica actual y abre nuevas vías para futuros dispositivos basados en funcionamiento bimodal.[CA] La fotònica de silici és una tecnologia emergent clau en xarxes de comunicació i interconnexions de centres de dades de nova generació, entre altres. El seu èxit es basa en la utilització de plataformes compatibles amb la tecnologia CMOS per a la integració de circuits òptics en dispositius diminuts per a una producció a gran escala a baix cost. Dins d'aquest camp, els interferòmetres integrats juguen un paper crucial en el desenvolupament de diverses aplicacions fotòniques en un xip com a sensors biològics, moduladors electro-òptics, commutadors totalment òptics, circuits programables o sistemes LiDAR, entre altres. No obstant això, és ben sabut que la interferometría òptica sol requerir camins d'interacció molt llargs, la qual cosa dificulta la seua integració en espais molt compactes. Per a mitigar algunes d'aquestes limitacions de grandària, van sorgir diversos enfocaments, incloent materials sofisticats o estructures més complexes, que, en principi, van reduir l'àrea de disseny però a costa d'augmentar els processos de fabricació i el cost. Aquesta tesi té com a objectiu proporcionar solucions generals al problema de grandària típica dels interferòmetres òptics integrats, amb la finalitat de permetre la integració densa de dispositius basats en silici. Per a això, combinem els beneficis tant de les guies d'ones bimodals com de les estructures periòdiques, en termes de funcionament d'alt rendiment per a dissenyar interferòmetres monocanal compactes en àrees molt reduïdes. Més específicament, investiguem els efectes dispersius que apareixen en estructures menors a la longitud d'ona i en les de cristall fotònic, per a la seua implementació en diferents configuracions interferomètriques bimodals. A més, vam demostrar diverses aplicacions potencials com a sensors, moduladors i commutadors en grandàries ultres compactes d'unes poques micres cuadrades. En general, aquesta tesi proposa un nou concepte d'interferòmetre integrat que aborda els requisits de grandària de la fotònica actual i obri noves vies per a futurs dispositius basats en funcionament bimodal.[EN] Silicon photonics is a key emerging technology in next-generation communication networks and data centers interconnects, among others. Its success relies on the ability of using CMOS-compatible platforms for the integration of optical circuits into small devices for a large-scale production at low-cost. Within this field, integrated interferometers play a crucial role in the development of several on-chip photonic applications such as biological sensors, electro-optic modulators, all-optical switches, programmable circuits or LiDAR systems, among others. However, it is well known that optical interferometry usually requires very long interaction paths, which hinders its integration in highly compact footprints. To mitigate some of these size limitations, several approaches emerged including sophisticated materials or more complex structures, which, in principle, reduced the design area but at the expense of increasing fabrication process steps and cost. This thesis aims at providing general solutions to the long-standing size problem typical of optical integrated interferometers, in order to enable the densely integration of silicon-based devices. To this end, we combine the benefits from both bimodal waveguides and periodic structures, in terms of high-performance operation and compactness to design single-channel interferometers in very reduced areas. More specifically, we investigate the dispersive effects that arise from subwavelength grating and photonic crystal structures for their implementation in different bimodal interferometric configurations. Furthermore, we demonstrate various potential applications such as sensors, modulators and switches in ultra-compact footprints of a few square microns. In general, this thesis proposes a new concept of integrated interferometer that addresses the size requirements of current photonics and open up new avenues for future bimodal-operation-based devices.Financial support is also gratefully acknowledged through postdoctoral FPI grants from Universitat Politècnica de València (PAID-01-18). European Commission through the Horizon 2020 Programme (PHC-634013 PHOCNOSIS project). The authors acknowledge funding from the Generalitat Valenciana through the AVANTI/2019/123, ACIF/2019/009 and PPC/2020/037 grants and from the European Union through the operational program of the European Regional Development Fund (FEDER) of the Valencia Regional Government 2014–2020.Torrijos Morán, L. (2021). Photonic Applications Based on Bimodal Interferometry in Periodic Integrated Waveguides [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172163TESISCompendi