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Traducció de: Photonics : an introductory course, Descripció del recurs: 5 juliol 2024, La fotònica treballa les aplicacions de la llum a la ciència i la tecnologia, incloent un gran ventall de temàtiques, que van des de l’enginyeria fins a les telecomunicacions, la medicina, la informàtica, la metrologia i molts més. Aquest llibre aborda diversos temes relacionats amb les propietats de la interacció coherent de la llum amb la matèria dins del marc de l’electrodinàmica clàssica, introduint els conceptes bàsics als estudiants de pregrau i als joves investigadors que s’interessen per aquest camp. El contingut inclou una revisió de les propietats fonamentals de la llum i de la teoria clàssica de l’emissió de llum, i introdueix també les equacions bàsiques que descriuen la propagació de feixos i els polsos de llum, així com la propagació de la llum en cristalls uniaxials i la difracció. A l’acabament de cada capítol, s’hi inclou una llista de problemes resolts i, per a aquells estudiants que vulguin aprofundir en els conceptes fascinants d’aquest camp, la bibliografia que trobaran al final abasta tant la literatura bàsica com la més especialitzada., 1

Quantum Key Distribution (QKD) is a technique that provides perfect secrecy for communication systems, which is crucial against quantum computers capable of breaking current public-key cryptosystems. QKD is becoming a mature technology but it still suffers from implementation problems due to imperfections on real hardware that soften it’s security. To correct those is necessary to develop error mitigation mechanisms, as well as security by design through use of two-photon protocols. In this Thesis, we combine these two approaches in fiber-based QKD, particularizing for evolved fibers with improved data bandwidths. At the same time, we emphasize integration with quantum photonics, and carry out actual microfabrication of basic elements in the laboratory for future QKD applications.

Current streetlights using LED emitters are primarily designed for efficient illumination of an area, but do not commonly consider visual comfort parameters, which are necessary to prevent glare and eye discomfort. This report outlines the design of a streetlight that prioritizes the maximum visual comfort for pedestrians while incorporating a novel optical packaging technology for the light emitter. We present the design considerations, including visual comfort parameters and requirements, as well as the methodology used to achieve this objective. Finally, a prototype design that fulfils the specified criteria is presented.

Due to the magnetic intrinsic divergence present in the magnetic field, which makes it difficult to transmit efficiently from one point to another low frequency magnetic fields, the signal decays rapidly. In addition, current centimetre-scale sensors can detect the signal transmission of many particles, but not a small number or a single particle. This matter has been improved by researching and enhancing the transmission medium, by decreasing signal divergence decreases signal attenuation in the magnetic field and resolves the issue of size differences. Magnetic fields have been generated in the laboratory by constructing a circuit, and analyse and compare ferrite, Nickel, and cobalt as magnetic materials. Numerous experiments demonstrate that the magnetic guide effectively reduces the magnetic field's attenuation, and that the transmission efficacy decreases as the size of the magnetic guide increases. Moreover, compared various sizes, the transmission of high-frequency signals in the magnetic field is significantly enhanced, whereas the transmission of low-frequency signals is not enhanced.

This study explores the polarimetric properties of various turbid media, including biological tissues, using Mueller matrix imaging. It addresses the challenges associated with detecting and measuring the small polarimetric signals characteristic of highly scattering media, providing valuable insights into tissue behavior. Furthermore, the study seeks to develop a procedure for restoring visibility in this type of media by utilizing the polarization information encoded in the Mueller matrix. Backscattering Mueller matrix imaging was employed to measure the polarimetric properties of the different samples, while the differential decomposition method was utilized for the analysis of the data obtained. All experiments were conducted using a consistent instrument setup to ensure reliable and comparable analysis across the diverse samples.

Quantum topological photonics has the potential to improve quantum information transmission without decoherence. In order to investigate what is the role of topology in the propagation of quantum states of light, we study one- and two-mode squeezing distribution and its robustness against random disorder in a topological photonic lattice that mimics the Su-Schrieffer-Heeger (SSH) model following the lines of an existing study. To truly separate the effect of nontrivial topology from regular localization, we compare a topological edge state in a SSH model with an impurity-induced localized state in a topologically trivial lattice. We find that the phase of the quadrature of the one-mode squeezed light is preserved along the propagation for both systems in the absence of random disorder. We also see that squeezing acquires the spatial distribution of the topologically protected state. When random disorder is added, we find that the phase of the quadrature of one-mode squeezed light is only preserved in the SSH system as long as chiral symmetry is preserved, unlike in the impurity system, where the phase of the quadrature of one-mode squeezed light rotates upon any type of disorder.

Eye movements have been shown to be altered in neurological disorders with eye-tracking technology, and thus it has been recently proposed to use them as biomarkers for their early diagnosis. The eye-tracker EyeLink 1000 Plus is the current Gold Standard to record eye movements but has some limitations to be used in a clinical environment. The purpose of this work was to compare the performance of a new, less complex eye-tracker, the Tobii Pro Spectrum, with the EyeLink 1000 Plus for screening purposes. To do so, both eye-trackers were used to record eye movements of 10 participants when performing several visual tasks (saccades, smooth pursuit and fixation). A software was implemented to display the visual stimuli on a screen and to acquire and process the data with the Tobii Pro Spectrum. The results and the statistical analysis carried out suggest that both eye-trackers provide similar data for most of the parameters analysed, meaning that the Tobii Pro Spectrum is a useful tool to record eye movements with a precision similar to that of the Gold Standard and thus, that it could be used for clinical analyses.

© 2023 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., We propose a self-cleaning mechanism in linear non-Hermitian graded index multimode fibers. The proposal is based a unidirectional coupling among transverse modes, induced by the introduction of a non-Hermitian potential, i.e. by the simultaneous modulation of the propagation constant and of the gain/loss coefficient along the fiber. The effect is semi-analytically predicted on a simplified Gaussian beam approximation and numerically proven by solving the wave propagation equation. As the main result, we demonstrate a substantial condensation of the radiation into the lowest order mode; resulting in a linear non-Hermitian self-cleaning. The demonstrated scheme could be experimentally realized within the current nanofabrication technologies., Peer Reviewed, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Postprint (author's final draft)

Liquid crystal (LC) is a unique state of matter that exhibits properties of both liquids and solids. One main property is that the nematic phase allows the possibility to orientate and align molecules in any direction by application of external perturbations such as electric, magnetic field, heat or pressure. This thesis will study the implementation of LC waveguide samples and its characterization at normal incidence light in a transmission optical setup in two different ways: in-plane (azimuthal rotation) and out-of-plane (polar rotation). This will provide a holistic approach for electro-optical characterization on the change in azimuthal and polar angles of the nematic LC waveguide with reference to the applied voltage.

The luminescence of (nano)materials is often sensitive to temperature. This enables thermometry experiments with micrometer resolution by simply inserting this type of thermometers in a relevant sample, followed by remote acquisition of the emission spectrum. The development of luminescent thermometers is mainly focused on the maximization of spectral changes for small temperature variations. However, it is still unclear how luminescent thermometers perform in the actual application. In this thesis, we have investigated the experimental errors of luminescent thermometers to better understand what affects the reliability of temperature measurements. Our work shows how errors due to noise, introduced by the photodetector, determine the uncertainty in the measured temperature. We further observed systematic errors in the measured temperature during our measurements with micrometer spatial resolution, which we attribute to the local photonic environment of the thermometer. In addition, we have examined methods to extend the temperature range of luminescent thermometers and developed new materials to achieve this. Our research shows that thermometer design is crucial for minimizing both measurement uncertainties and systematic errors. These insights can help to optimize new and existing thermometers, which is an important step for reliable application.

The silicon industry stands as a cornerstone in the realm of modern technology, underpinning an array of innovations that have reshaped the communication paradigm. Among its many contributions, silicon’s integration into photonics has revolutionised optical communications, enabling the development of high-performance devices and systems, and its commercialisation at an industrial level. At the heart of this transformative journey lies the grating coupler, an essential component that facilitates the seamless integration between silicon-based integrated waveguide devices and the vast world of optical fibers and free-space optics. This thesis analyses the design process of a grating coupler and its automatic optimisation.

En este trabajo se estudian los fenómenos de desexcitación espontánea que ocurren en sistemas con un gran número de átomos excitados. Primero se explica este fenómeno a partir de los estudios realizados por Dicke, quien describió por primera vez ese fenómeno cuántico, donde se proporcionan una manera de clasificar y ordenar los estados del sistema según su tasa de desexcitación. Después, se estudia la aparición de fenómenos de desexcitación en redes atómicas lineales. Seguidamente, se calcula de forma analítica la tasa de desexcitación del estado simétrico en una red triatómica en dos configuraciones espaciales: átomos dispuestos en fila, y átomos dispuestos en los vértices de un triángulo equilátero. Como resultado de este cálculo, se demuestra que la tasa de decaimiento coincide con la predicha por Dicke solo en el caso de la disposición triangular. Por último, para complementar el estudio de los estados colectivos, se estima la energía del estado superradiante de una red pentatómica mediante un algoritmo variacional implementado en un ordenador cuántico. Solo se obtuvieron resultados precisos cuando se ejecutó en un simulador ideal, aunque se proponen mejoras en el tratamiento del ruido derivado de la ejecución en un ordenador real., Departamento de Teoría de la Señal y Comunicaciones e Ingeniería Telemática, Departamento de Física Teórica, Atómica y Óptica, Grado en Física

El camp de la fotònica està avançant a grans passes, amb la promesa de noves tecnologies que podrien ser implementades en dispositius que usem en el dia a dia. Perquè això sigui una realitat, es necessiten desenvolupar nous materials per tal d’aprofitar les propietats de la llum. Això, tanmateix, planteja tota mena de reptes, però encara és possible trobar estructures que puguin ser útils. A més, la implementació d’algoritmes dins d’aquests propis dispositius serà certament un objectiu de la investigació dels pròxims anys. Aquest treball està dividit en dues parts, ambdues relacionades amb tecnologies de la fotònica experimental. A la primera part, detallem la fabricació i caracterització de diferents dispositius nanofotònics utilitzant el mètode ImpFab, una tècnica innovadora de nanofabricació en 3D. Primer, presentem la teoria darrere dels cristalls fotònics i els metamaterials, que després fabriquem utilitzant aquest mètode. Les mesures experimentals són posteriorment comparades amb dades teòriques simulades amb l’objectiu de caracteritzar les diferents propietats dels materials fabricats. Finalment, discutim possibles millores de l’estat d’aquesta tècnica. Per l’altra banda, a la segona part estudiem un sistema de fibres òptiques que reprodueix el comportament de l’anomenat quantum walk en una dimensió. Fem una descripció teòrica rigorosa dels aspectes matemàtics del quantum walk i com es pot traslladar a un sistema fotònic, seguit de la descripció del nostre experiment en concret. Demostrem la possibilitat de reproduir les distribucions generades en un quantum walk fent servir elements per fibres òptiques i com modificar el sistema per induir diferents efectes., El campo de la fotónica está avanzando a grandes pasos, con la promesa en el horizonte de nuevas tecnologías que podrían ser implementadas en nuestros dispositivos de uso cotidiano. Para que esto sea una realidad, se necesitan desarrollar nuevos materiales con tal de aprovechar las propiedades de la luz. Esto, no obstante, plantea toda clase de retos, aunque todavía es posible encontrar estructuras que puedan ser útiles para este propósito. Además, la implementación de algoritmos dentro de estos dispositivos será sin duda un objetivo para la investigación de los próximos años. Este trabajo está dividido en dos partes, ambas relacionadas con tecnologías de la fotónica experimental. En la primera parte, detallaremos la fabricación y caracterización de diferentes dispositivos nanofotónicos usando el método ImpFab, una técnica innovadora de nanofabricación en 3D. Primero presentamos la teoría relacionada con los cristales fotónicos y metamateriales, que luego fabricaremos usando este método. Las mediciones experimentales son posteriormente comparadas con datos teóricos simulados con el objetivo de caracterizar las distintas propiedades de los materiales fabricados. Finalmente, discutimos posibles mejoras de esta técnica. Por otro lado, en la segunda parte estudiaremos un sistema de fibras ópticas que reproduce el comportamiento del llamado quantum walk en una dimensión. Llevamos a cabo una descripción teórica de los aspectos matemáticos de un quantum walk y estudiamos como se traslada a un sistema fotónico, seguido de la descripción de nuestra implementación experimental. Demostramos la posibilidad de reproducir las distribuciones de un quantum walk usando elementos para fibras ópticas y cómo modificar el sistema para inducir diferentes efectos., The field of photonics is now advancing at a considerable speed, promising great technologies that could be soon implemented in our everyday devices. For this to become a reality, new materials need to be engineered in order to leverage the properties of light. This comes with many challenges, but it is still possible to fabricate structures that harness that power. The implementation of algorithms running on these photonic devices will certainly be pursued in the coming years. This work is divided into two subprojects related to technologies in experimental photonics. In Part 1, we will detail the fabrication and characterization of different nanophotonic devices using Implosion Fabrication, a novel 3D nanofabrication technique. First, we present the theory behind photonic crystals and metamaterials, which we later fabricated using this method. The experimental measurements are then matched with data from simulations to characterize the properties of the fabri- cated materials. Optimizations to the framework are discussed. In Part 2 we study an optical fiber photonic system that reproduces the distribution of a one-dimensional quantum walk on a discrete lattice. We discuss a theoretical review of the mathematical aspects of a quantum walk and its translation to a photonic system, followed by a description of our experimental implementation. We demonstrate the feasibility of reproducing quantum walk distributions using fiber optic elements and how to further modify the system to induce different effects on the walk., Outgoing

The development of coherent high density WDM PONs, forecasted as one of the promising technologies to increase the spectral efficiency and reduce the energy consumption, can be obstructedbythe limited tunability, high wavelength drifts and tuning transients of the DFB lasers used in PONs. In this work, a new non-intrusive, colorless and scalable channel allocation procedure is experimentally validated using simple EML lasers as transmitters and local oscillators., Peer Reviewed, Postprint (author's final draft)

Quantum Key Distribution (QKD) is a crucial step in quantum cryptography protocols, as a secure distribution of the secret key is determinant in the performance of the system. Some QKD protocols like E91 require the distribution of entangled photon pairs between the emitter and the receiver in order to guarantee a safe transfer of information. However, the distribution of entangled quantum states is a remarkably challenging task, due to the fragility of this physical phenomenon. In this project, a new method for the distribution of high-dimensional entangled photon pairs through an optical fiber is presented. This method is based on the spatial modulation of the output beam of an Entangled Photon Source (EPS) in order to increase the coupling efficiency into a multi-core optical fiber (MCF), which otherwise is highly inefficient. In order to perform the spatial modulation, a LCoS phase-only Spatial Light Modulator (SLM) has been used. The presented method is designed for the modulation of a two-dimensional entangled photon beam, both entangled spatially and in polarization. So, the aim is not only to improve the overall single photon efficiency, but also the maximize as much as possible the coupling of entangled photon pairs, always maintaining the spatial correlations and the polarization entanglement. The system has been tested for a 810$nm$ (NIR) central wavelength EPS, coupled into a 1m long MCF. The obtained results for the single photon efficiency are not as good as initially expected, due to limitations found in the setup along the course of the experiment. Nevertheless, the spatial correlation maintenance and the efficiency in the coupling of entangled photon pairs compared to the obtained single photon efficiency have resulted to be remarkable. The overall conclusion of this project is that the presented method has the potential to achieve much higher coupling efficiencies with some changes in the setup, always maintaining the entanglement. The versatility, La Quantum Key Distribution (QKD) es un paso crucial en protocolos de criptografía cuántica, ya que una distribución segura de la clave secreta es determinante en el rendimiento del sistema. Algunos protocolos de QKD como el E91 requieren la distribución de pares de fotones entrelazados entre el emisor y el receptor por tal de garantizar la transferencia segura de información. No obstante, la distribución de estados cuánticos entrelazados es un reto considerable, debido a la fragilidad de este fenómeno físico. En este proyecto, un nuevo método es presentado para la distribución de pares de fotones entrelazados en múltiples dimensiones a través de una fibra óptica. Este método se basa en la modulación espacial de la salida de una fuente de fotones entrelazados (EPS) por tal de incrementar la eficiencia de acople en una fibra milti-core (MCF), que de otra forma sería muy ineficiente. Para aplicar la modulación espacial, se ha utilizado un Spatial Light Modulator (SLM) de LCoS únicamente en fase. El método presentado ha sido diseñado para la modulación de un haz de fotones entrelazados en dos dimensiones, tanto espacialmente como en polarización. Por tanto, el objetivo no es solamente mejorar la eficiencia de acople de fotones individuales, sino también maximizar tanto como sea posible el acople de pares de fotones entrelazados, siempre manteniendo las correlaciones espaciales y el entrelazamiento en polarización. El sistema ha sido probado para una EPS centrada en la frecuencia de 810nm (NIR), acoplada a una MCF de 1m de largo. Los resultados obtenidos para la eficiencia de fotones individuales no es tan buena como se esperaba, debido a limitaciones encontradas durante el transcurso del experimento. No obstante, la conservación de las correlaciones i la eficiencia de acople de pares de fotones entrelazados comparadas con la eficiencia de fotones individuales han resultado ser muy remarcables. La conclusión general de este proyecto es que el método presentado tiene el, La Quantum Key Distribution (QKD) és un pas crucial en protocols de criptografia quàntica, ja que una distribució segura de la clau secreta és determinant en el rendiment del sistema. Alguns protocols de QKD com l'E91 requereixen la distribució de parells de fotons entrellaçats entre l'emissor i el receptor per tal de garantir la transferència segura d'informació. No obstant, la distribució de estats quàntics entrellaçats és un repte important, degut a la fragilitat d'aquest fenomen físic. En aquest projecte, un nou mètode per a la distribució de parells de fotons entrellaçats en múltiples dimensions a través de fibra òptica és presentat. Aquest mètode es basa en la modulació espacial de la sortida d'una font de fotons entrellaçats (EPS) per tal d'incrementar l'eficiència d'acoblament en una fibra multi-core (MCF), que altrament seria molt ineficient. Per tal de aplicar la modulació espacial, s'ha utilitzat un Spatial Light Modulator (SLM) de LCoS únicament en fase. El mètode presentat ha estat dissenyat per a la modulació d'un feix de fotons entrellaçats en dues dimensions, tant espacialment com en polarització. Per tant, l'objectiu no és solament millorar l'eficiència d'acoblament de fotons individuals, sinó també maximitzar tant com es pugui l'acoblament de parells de fotons entrellaçats, sempre mantenint les correlacions espacials i l'entrellaçament en polarització. El sistema ha estat provat per a una EPS amb una longitud d'ona central de 810nm (NIR), acoblada a una MCF de 1m de llarg. Els resultats obtinguts per a l'eficiència de fotons individuals no són tan bons com s'esperava, degut a limitacions trobades durant el transcurs de l'experiment. No obstant, la conservació de les correlacions i l'eficiència en l'acoblament de parells de fotons entrellaçats comparades amb l'eficiència de fotons individuals han resultat ser molt remarcables. La conclusió general d'aquest projecte es que el mètode presentat té el potencial per aconseguir eficiències molt més elevad

Optical properties of photonic crystals have emerged as being pivotal in the field of nanophotonics. Their artificial periodicity can alter and create new effective dispersion relations compared to bulk materials, allowing us to control the flow of light and light-matter interactions. Specifically, the enhancement of the electromagnetic field obtained either at the surface or inside the nanostructure is very important for applications in optical sensing or light emission. In particular, it is known that by gradually varying the period of the PhC in the direction of propagation of light, a process known as chirping the samples, different wavelengths are localised at different positions in the crystal. This wavelength dependant light localisation has been demonstrated numerically in one and two dimensions in the literature, but there has been little work done to study the phenomenon in three dimensions and experimentally. This project has studied the wavelength dependent localisation of light in chirped woodpile PhC samples in the visible and infrared, both from a numerical and experimental point of view. In the end, a qualitative match between simulations and experiments has been obtained. These structures, in combination with different types of absorptive materials placed at the surface or at particular positions inside the structure target application in sensing., Las propiedades ópticas de cristales fotónicos han resultado ser clave en el campo de la nano-fotónica. Su periodicidad, creadas artificialmente, nos permite diseñar nuevas relaciones de dispersión efectivas, imposibles de obtener en materiales convencionales. Esto nos permite controlar el flujo de luz y las interacciones luz-materia. Concretamente, la amplificación del campo electromagnético en la superficie o dentro de la estructura manométrica es crucial en aplicaciones relacionadas con sensores ópticos y emisión de luz. En particular, se sabe que variando gradualmente el periodo de los cristales en la dirección de propagación de la luz, un proceso conocido como añadir "chirp" en los cristales, diferentes longitudes de onda se localizan en diferentes posiciones dentro de los cristales. Esta localización en función de la longitud de onda se ha estudiado sobre todo numéricamente en cristales de una o dos dimensiones, sin embargo, pocos estudios han estudiado el fenómeno de manera experimental o en cristales tridimensionales. Específicamente este proyecto se ha centrado en la caracterización de cristales "woodpile" en el visible y en el infrarrojo, tanto experimental como numéricamente. Finalmente, se ha llegado a una relación cualitativa entre simulaciones y experimentos. Creemos que estas estructuras, combinadas con diferentes tipos de materiales absorbentes situados en la superficie o en posiciones concretas dentro de los cristales, pueden tener aplicaciones en sensores., Les propietats òptiques dels cristalls fotònics han resultat ser clau en el camp de la nano-fotònica. La seva periodicitat, creada artificialment, ens permet dissenyar noves relacions de dispersió efectives, impossibles d'obtenir en materials convencionals. Això ens permet controlar el flux de llum i les interaccions llum-matèria. Concretament, l'amplificació del camp electromagnètic a la superfície o dins l'estructura nanomètrica és crucial en aplicacions relacionades amb sensors òptics i emissió de llum. En particular, se sap que fent variar gradualment el període dels cristalls en la direcció de propagació de la llum, procés conegut com a afegir "chirp" als cristalls, diferents longituds d'ona es localitzen a diferents posicions dins els cristalls. Aquesta localització en funció de la longitud d'ona ha estat comprovada numèricament en cristalls d'una o dues dimensions, però pocs estudis han estat fets de cara a estudiar el fenomen experimentalment o cristalls tridimensionals. Aquest projecte s'ha centrat en la caracterització de cristalls woodpile en el visible i l'infraroig, tan experimental com numèricament. Finalment, s'ha aconseguit arribar a una relació qualitativa entre simulacions i experiments. Creiem que aquestes estructures, combinades amb diferents tipus de materials absorbents situats a la superfície o en posicions concretes dins els cristalls tenen potencials aplicacions com a sensors.

Super-resolution techniques such as STED and RESOLFT rely on the scanning of a sample with a Laguerre-Gaussian (doughnut) beam. One of their main limitations is speed since the sample has to be scanned point by point. In this thesis, I introduce a setup using acoustic-optic deflectors (AODs) to create a matrix of scanning beams and illuminate a sample at multiple points simultaneously. The setup uses a two path scheme in order to illuminate the sample either using Gaussian or doughnut beams. For this, the doughnut after passing the AOD is characterized and a subtraction microscopy method is implemented, allowing the capture of super-resolution images. This method can in the future be used to parallelize techniques such as STED and RESOLFT and will be an important step in the development of a live-cell nanoscopy technique.

High-resolution time measurement is a fundamental building block on a wide variety of applications such as time-of-flight based systems, single-photon microscopy and quantum communications. FPGA-based TDCs are the preferred choice for cost-effective implementations requiring both high performance and flexibility. In this work, a Tapped-Delay Line (TDL) and Wave Union Tapped-Delay Line (WU TDL) TDC architectures are implemented and characterized on a Zynq Ultrascale+ FPGA-board. The characterization will mainly focus on determining the resolution and linearity of both TDCs. A bin merging algorithm is also tested to see the increment of linearity at expense of resolution. The TDL and WU TDL implementations were tested measuring the time difference of two signals obtaining 11.6 ps and 11.4 ps RMS resolution respectively. The achieved performance allow the proposed implementations to be integrated in high-resolution time measuring systems., La mesura de temps a alta resolució és un dels blocs fonamentals en un gran ventall d'aplicacions com els sistemes basats en temps de vol (TOF), la microscòpia d'un sol fotó o les comunicacions quàntiques. Els TDCs basats en FPGAs són l'opció preferida per implementacions de baix cost que requereixin d'alt rendiment i flexibilitat. En aquest treball, les arquitectures TDC Tapped-Delay Line (TDL) i Wave Union Tapped-Delay Line (WU TDC) són implementades i caracteritzades en una placa FPGA Zynq Ultrascale+. La caracterització es centrarà principalment en determinar la resolució i la linealitat d'ambdós TDCs. A més, s'ha provat un algoritme d'agrupació de bins per observar l'increment de linealitat en detriment de la resolució. Les implementacions TDL i WU TDL varen ser provades mesurant la diferencia temporal de dos senyals, obtenint-ne una resolució RMS de 11.6 ps i 11.4 ps respectivament. El rendiment obtingut permet integrar les implementacions proposades en sistemes de mesura de temps d'alta resolució.

Photon antibunching is a fundamental quantum phenomenon in the field of quantum optics, which plays a crucial role in quantum information and telecommunication applications. The aim of this project is to design and implement from scratch the experimental setup to measure antibunching behaviour in quantum dots. The intended purpose is to make this setup accessible to future students of the Quantum Science and Technology master's laboratory by the upcoming year. In this study, we investigate CdSe/ZnS quantum dots as single-photon emitters, a versatile semiconductor nanocrystal that facilitates the measurement of quantum correlations. The initial step involves characterizing the quantum dot to determine the necessary parameters for designing the optical system. Successful execution of this experiment will provide students with enhanced comprehension of the optical properties of quantum dots and the sub-Poissonian statistics governing photon antibunching phenomena.

Optically pumped magnetometers (OPMs) have gained attention in recent years for their medical application in magnetoencephalography(MEG), a neuro-imaging technique that maps brain activity by measuring the magnetic fields produced by the brain's electrical currents. Addressing the current challenges of OPMs, including their size and cost, is imperative to making them a scalable solution for MEG. The focus of this project lies in enhancing the micro-fabricated micro-electromechanical systems (MEMs) vapor cells integral to OPMs by the incorporation of thin-film platinum resistive heaters. The functionality of these integrated heaters was qualified through spectroscopy and zero field resonance measurements. The calibration process yielded successful results that were compared against values given by the vapor's absorption spectrum. Additionally, effective packaging for magnetometry was achieved, evident in the zero field resonance spectrum, where compensation fields were identified and visualized through a heat map.

We observe linear and nonlinear light localization at the edges and in the corners of truncated moiré arrays created by the superposition of periodic mutually twisted at Pythagorean angles square sublattices. Experimentally exciting corner linear modes in the femtosecond-laser written moiré arrays we find drastic differences in their localization properties in comparison with the bulk excitations. We also address the impact of nonlinearity on the corner and bulk modes and experimentally observe the crossover from linear quasilocalized states to the surface solitons emerging at the higher input powers. Our results constitute the first experimental demonstration of localization phenomena induced by truncation of periodic moiré structures in photonic systems., This research is funded by the research Project No. FFUU- 2021-0003 of the Institute of Spectroscopy of the Russian Academy of Sciences and partially funded by the RSF Grant No. 21-12-00096. F. Y. acknowledges support from Shanghai Outstanding Academic Leaders Plan (Grant No. 20XD1402000) and the NSFC (Grant No. 91950120). S. K. I. and L. T. acknowledge support by Grants No. CEX2019-000910-S and No. PGC2018-097035-B-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER, Fundació Cellex, Fundació Mir-Puig, and Generalitat de Catalunya (CERCA)., Peer Reviewed, Postprint (published version)

Taming the instabilities inherent to many nonlinear optical phenomena is of paramount importance for modern photonics. In particular, the so-called snake instability is universally known to severely distort localized wave stripes, leading to the occurrence of transient, short-lived dynamical states that eventually decay. This phenomenon is ubiquitous in nonlinear science—from river meandering to superfluids—and so far it apparently remains uncontrollable; however, here we show that optical snake instabilities can be harnessed by a process that leads to the formation of stationary and robust two-dimensional zigzag states. We find that such a new type of nonlinear waves exists in the hyperbolic regime of cylindrical microresonators, and that it naturally corresponds to two-dimensional frequency combs featuring spectral heterogeneity and intrinsic synchronization. We uncover the conditions of the existence of such spatiotemporal photonic snakes and confirm their remarkable robustness against perturbations. Our findings represent a new paradigm for frequency comb generation, thus opening the door to a whole range of applications in communications, metrology and spectroscopy., Peer Reviewed, Postprint (author's final draft)

[ES] La tomografía por difracción surge para mejorar las técnicas de imagen al considerar la naturaleza ondulatoria de la luz. Mientras que los primeros sistemas de imagen médica se basaban únicamente en fuentes sin difracción, este enfoque consigue mejorar la reconstrucción del índice de refracción de los objetos, lo que permite, por ejemplo, el estudio de estructuras subcelulares. Del mismo modo, la demanda de redes de telecomunicaciones cada vez más rápidas y seguras ha propiciado la aparición de la fotónica. Hace dos décadas, la combinación de estos dos campos dio lugar a los primeros sistemas de tomografía por difracción óptica (ODT), los cuáles han evolucionado rápidamente durante este siglo. En esta tesis, presentamos dos nuevas aplicaciones de la ODT. La primera está relacionada con el concepto del microscopio tomográfico de fase (TPM), una versión de la ODT que permite el estudio de células aisladas, con muchas aplicaciones biomédicas, como el diagnóstico y la prognosis del cáncer. Sin embargo, los sistemas TPM actuales son caros, pesados y complejos. Para resolver estos problemas, proponemos el concepto de TPM en chip. Con este fin, diseñamos una hoja de ruta hacia el primer dispositivo tomográfico integrado en el marco de la tecnología lab-on-a-chip (LoC), y desarrollamos los primeros pasos para ello: 1) Hasta ahora, sólo se han utilizado detectores planos para obtener los mapas de índice de refracción de los objetos estudiados en TPM, basados en la detección del campo difractado hacia delante. Sin embargo, los principios físicos fundamentales indican que medir también el campo difractado hacia detrás debería mejorar la resolución de las imágenes. Además, un detector plano no es la configuración óptima para el TPM en chip. En esta línea, hemos explorado la posibilidad de usar detectores circulares en este escenario, como una técnica más adecuada para las configuraciones en chip, demostrando al mismo tiempo que este enfoque proporciona una mejor resolución, [CA] La tomografia per difracció sorgeix per millorar les tècniques d'imatge anteriors en considerar la naturalesa ondulatòria de la llum. Mentre que els primers sistemes d'imatge mèdica es basaven únicament en fonts sense difracció, aquest enfocament aconsegueix millorar la reconstrucció de l'índex de refracció dels objectes, la qual cosa permet, per exemple, l'estudi d'estructures subcelulars. De la mateixa manera, la demanda de xarxes de telecomunicacions cada vegada més ràpides i segures ha propiciat l'aparició de la fotònica. Fa dues dècades, la combinació d'aquests dos camps va portar als primers sistemes de tomografia per difracció òptica (ODT), els quals han evolucionat ràpidament durant aquest segle. En aquesta tesi, presentem dues noves aplicacions de la ODT. La primera està relacionada amb el concepte del microscopi tomogràfic de fase (TPM), una versió de la ODT que permet l'estudi de cèl·lules aïllades, amb moltes aplicacions en biomedicina, com el diagnòstic i prognosi del càncer. No obstant això, els sistemes TPM actuals són cars, pesats i complexos. Per resoldre aquests problemes, proposem el concepte de TPM en xip. Per fer-ho, dissenyem un full de ruta cap al primer dispositiu tomogràfic integrat en el marc de la tecnologia lab-on-a-chip (LoC), i desenvolupem els primers passos a aquest efecte: 1) Fins ara, només s'han utilitzat detectors plans per a obtindre els mapes d'índex de refracció dels objectes estudiats en TPM, basats en la detecció del camp difractat cap avant. No obstant això, els principis físics fonamentals indiquen que mesurar també el camp difractat cap endarrere hauria de millorar la resolució de les imatges. A més, un detector pla no és la configuració òptima per al TPM en xip. En aquesta línia, hem explorat la possibilitat d'usar detectors circulars en aquest escenari, com una tècnica més adequada per a les configuracions en xip, demostrant al mateix temps que aquest enfocament proporciona una millor resolució que el lineal. 2) Pro, [EN] Diffraction Tomography arises to improve previous imaging techniques by considering the wave nature of light. Whereas the first medical imaging systems relied only on non-diffracting sources, this approach results in an enhanced reconstruction of the object's refractive index distribution, allowing, for example, the study of subcellular structures. Likewise, the demand for increasingly faster and secure telecommunication networks led to the advent of photonics. Two decades ago, the combination of these two fields gave rise to the first optical diffraction tomography (ODT) systems, which have rapidly evolved during this century. In this thesis, we present two novel applications of ODT. The first one is related to the concept of tomographic phase microscopy (TPM), a version of ODT that enables the study of isolated cells, with many applications in biomedicine, such as the diagnosis and prognosis of cancer. Nevertheless, current TPM systems are expensive, heavy, and cumbersome. To solve these issues we propose the concept of on-chip TPM. For this purpose, we design a roadmap towards the first integrated tomographic device in the frame of lab-on-a-chip (LoC) technology and develop the first steps to this end: 1) Until now, only flat detectors have been used to obtain the refractive index maps of the objects studied in TPM, based on the detection of the forward scattering. However, fundamental physical principles indicate that measuring also the backscattered field should improve the resolution of the images. Moreover, a flat detector is not the optimal configuration for on-chip TPM. In this vein, we have explored the possibility of using circular detectors in this scenario as a more suitable technique for on-chip configurations, demonstrating at the same time that this approach provides a better resolution than the linear one. 2) We propose a TPM on-chip scheme based on the use of dielectric nanoantennas as the ODT light source and detector pixels, and experimental