Towards efficient three-dimensional wide-angle beam propagation methods and theoretical study of nanostructures for enhanced performance of photonic devices

In this dissertation, we have proposed a novel class of approximants, the so-called modified Padé approximant operators for the wide-angle beam propagation method (WA-BPM). Such new operators not only allow a more accurate approximation to the true Helmholtz equation than the conventional operators, but also give evanescent modes the desired damping. We have also demonstrated the usefulness of these new operators for the solution of time-domain beam propagation problems. We have shown this both for a wideband method, which can take reflections into account, and for a split-step method for the modeling of ultrashort unidirectional pulses. The resulting approaches achieve high-order accuracy not only in space but also in time. In addition, we have proposed an adaptation of the recently introduced complex Jacobi iterative (CJI) method for the solution of wide-angle beam propagation problems. The resulting CJI-WA-BPM is very competitive for demanding problems. For large 3D waveguide problems with refractive index profiles varying in the propagation direction, the CJI method can speed-up beam propagation up to 4 times compared to other state-of-the-art methods. For practical problems, the CJI-WA-BPM is found to be very useful to simulate a big component such as an arrayed waveguide grating (AWG) in the silicon-on-insulator platform, which our group is looking at. Apart from WA beam propagation problems for uniform waveguide structures, we have developed novel Padé approximate solutions for wave propagation in graded-index metamaterials. The resulting method offers a very promising tool for such demanding problems. On the other hand, we have carried out the study of improved performance of optical devices such as label-free optical biosensors, light-emitting diodes and solar cells by means of numerical and analytical methods. We have proposed a solution for enhanced sensitivity of a silicon-on-insulator surface plasmon interference biosensor which had been previously proposed in our group. The resulting sensitivity has been enhanced up to 5 times. Furthermore, we have developed an improved model to investigate the influence of isolated metallic nanoparticles on light emission properties of light-emitting diodes. The resulting model compares very well to experimental results. Finally, we have proposed the usefulness of core-shell nanostructures as nanoantennas to enhance light absorption of thin-film amorphous silicon solar cells. An increased absorption up to 33 % has theoretically been demonstrated

Integrated Inp Photonic Switches

Photonic switches are becoming key components in advanced optical networks because of the large variety of applications that they can perform. One of the key advantages of photonic switches is that they redirect or convert light without having to make any optical to electronic conversions and vice versa, thus allowing networking functions to be lowered into the optical layer. InP-based switches are particularly attractive because of their small size, low electrical power consumption, and compatibility with integration of laser sources, photo-detectors, and electronic components. In this dissertation the development of integrated InP photonic switches using an area-selective zinc diffusion process has been investigated. The zinc diffusion process is implemented using a semi-sealed open-tube diffusion technique. The process has proven to be highly controllable and reproducible by carefully monitoring of the diffusion parameters. Using this technique, isolated p-n junctions exhibiting good I-V characteristics and breakdown voltages greater than 10 V can be selectively defined across a semiconductor wafer. A series of Mach-Zehnder interferometric (MZI) switches/modulators have been designed and fabricated. Monolithic integration of 1x2 and 2x2 MZI switches has been demonstrated. The diffusion process circumvents the need for isolation trenches, and hence optical losses can be significantly reduced. An efficient optical beam steering device based on InGaAsP multiple quantum wells is also demonstrated. The degree of lateral current spreading is easily regulated by controlling the zinc depth, allowing optimization of the injected currents. Beam steering over a 21 microns lateral distance with electrical current values as low as 12.5 mA are demonstrated. Using this principle, a reconfigurable 1x3 switch has been implemented with crosstalk levels better than -17 dB over a 50 nm wavelength range. At these low electrical current levels, uncooled and d.c. bias operation is made feasible. The use of multimode interference (MMI) structures as active devices have also been investigated. These devices operate by selective refractive index perturbation on very specific areas within the MMI structure, and this is again realized using zinc diffusion. Several variants such as a compact MMI modulator that is as short as 350 µm, a robust 2x2 photonic switch and a tunable MMI coupler have been demonstrated

Large Core Three Branch Polymer Power Splitters

We report about three branch large core polymer power splitters optimized for connecting standard plastic optical fibers. A new point of the design is insertion of a rectangle-shaped spacing between the input and the central part of the splitter, which will ensure more even distribution of the output optical power. The splitters were designed by beam propagation method using BeamPROP software. Acrylic-based polymers were used as optical waveguides being poured into the Y-grooves realized by computer numerical controlled engraving on poly(methyl methacrylate) substrate. Measurement of the optical insertion losses proved that the insertion optical loss could be lowered to 2.1 dB at 650 nm and optical power coupling ratio could reach 31.8% : 37.3% : 30.9%

Multipurpose Programmable Integrated Photonics: Principles and Applications

[ES] En los últimos años, la fotónica integrada programable ha evolucionado desde considerarse un paradigma nuevo y prometedor para implementar la fotónica a una escala más amplia hacia convertirse una realidad sólida y revolucionaria, capturando la atención de numerosos grupos de investigación e industrias. Basada en el mismo fundamento teórico que las matrices de puertas lógicas programables en campo (o FPGAs, en inglés), esta tecnología se sustenta en la disposición bidimensional de bloques unitarios de lógica programable (en inglés: PUCs) que -mediante una programación adecuada de sus actuadores de fase- pueden implementar una gran variedad de funcionalidades que pueden ser elaboradas para operaciones básicas o más complejas en muchos campos de aplicación como la inteligencia artificial, el aprendizaje profundo, los sistemas de información cuántica, las telecomunicaciones 5/6-G, en redes de conmutación, formando interconexiones en centros de datos, en la aceleración de hardware o en sistemas de detección, entre otros. En este trabajo, nos dedicaremos a explorar varias aplicaciones software de estos procesadores en diferentes diseños de chips. Exploraremos diferentes enfoques de vanguardia basados en la optimización computacional y la teoría de grafos para controlar y configurar con precisión estos dispositivos. Uno de estos enfoques, la autoconfiguración, consiste en la síntesis automática de circuitos ópticos -incluso en presencia de efectos parasitarios como distribuciones de pérdidas no uniformes a lo largo del diseño hardware, o bajo interferencias ópticas y eléctricas- sin conocimiento previo sobre el estado del dispositivo. Hay ocasiones, sin embargo, en las que el acceso a esta información puede ser útil. Las herramientas de autocalibración y autocaracterización nos permiten realizar una comprobación rápida del estado de nuestro procesador fotónico, lo que nos permite extraer información útil como la corriente eléctrica que suministrar a cada actuador de fase para cambiar el estado de su PUC correspondiente, o las pérdidas de inserción de cada unidad programable y de las interconexiones ópticas que rodean a la estructura. Estos mecanismos no solo nos permiten identificar rápidamente cualquier PUC o región del chip defectuosa en nuestro diseño, sino que también revelan otra alternativa para programar circuitos fotónicos en nuestro diseño a partir de valores de corriente predefinidos. Estas estrategias constituyen un paso significativo para aprovechar todo el potencial de estos dispositivos. Proporcionan soluciones para manejar cientos de variables y gestionar simultáneamente múltiples acciones de configuración, una de las principales limitaciones que impiden que esta tecnología se extienda y se convierta en disruptiva en los próximos años.[CA] En els darrers anys, la fotònica integrada programable ha evolucionat des de considerarse un paradigma nou i prometedor per implementar la fotònica a una escala més ampla cap a convertir-se en una realitat sòlida i revolucionària, capturant l'atenció de nombrosos grups d'investigaciò i indústries. Basada en el mateix fonament teòric que les matrius de portes lògiques programable en camp (o FPGAs, en anglès), aquesta tecnología es sustenta en la disposición bidimensional de blocs units lògics programables (en anglès: PUCs) que -mitjançant una programación adequada dels seus actuadors de fase- poden implementar una gran varietat de funcionalitats que poden ser elaborades per a operacions bàsiques o més complexes en molts camps d'aplicació com la intel·ligència artificial, l'aprenentatge profund, els sistemes d'informació quàntica, les telecomunicacions 5/6-G, en xarxes de comutació, formant interconnexions en centres de dades, en l'acceleració de hardware o en sistemes de detecció, entre d'altres. En aquest treball, ens dedicarem a explorar diverses capatitats de programari d'aquests processadors en diferents dissenys de xips. Explorem diferents enfocaments de vanguardia basats en l'optimització computacional i la teoría de grafs per controlar i configurar amb precisió aquests dispositius. Un d'aquests enfocaments, l'autoconfiguració, tracta de la síntesi automática de circuits òptics -fins i tot en presencia d'efectes parasitaris com ara pèrdues no uniformes o crosstalk òptic i elèctric- sense cap coneixement previ sobre l'estat del dispositiu. Tanmateix, hi ha ocasions en les quals l'accés a aquesta información pot ser útil. Les eines d'autocalibració i autocaracterització ens permeten realizar una comprovació ràpida de l'estat del nostre procesador fotònic, el que ens permet obtener informació útil com la corrent eléctrica necessària per alimentar cada actuador de fase per canviar l'estat del seu PUC corresponent o la pèrdua d'inserció de cada unitat programable i de les interconnexions òptiques que envolten l'estructura. Aquests mecanisms no només ens permeten identificar ràpidament qualsevol PUC o área del xip defectuosa en el nostre disseny , sinó que també ens mostren una altra alternativa per programar circuits fotònics en el nostre disseny a partir de valors de corrent predefinits. Aquestes estratègies constitueixen un pas gegant per a aprofitar tot el potencial d'aquests dispositius. Proporcionen solucions per a gestionar centenars de variables i alhora administrar múltiples accions de configuració, una de les principals limitacions que impideixen que aquesta tecnología esdevingui disruptiva en els pròxims anys.[EN] In recent years, programmable integrated photonics (PIP) has evolved from a promising, new paradigm to deploy photonics to a larger scale to a solid, revolutionary reality, bringing up the attention of numerous research and industry players. Based on the same theoretical foundations than field-programmable gate arrays (FPGAs), this technology relies on common, two-dimensional integrated optical hardware configurations based on the interconnection of programmable unit cells (PUCs), which -by suitable programming of their phase actuators- can implement a variety of functionalities that can be elaborated for basic or more complex operation in many application fields, such as artificial intelligence, deep learning, quantum information systems, 5/6-G telecommunications, switching, data center interconnections, hardware acceleration and sensing, amongst others. In this work, we will dedicate ourselves to explore several software capabilities of these processors under different chip designs. We explore different cutting-edge approaches based on computational optimization and graph theory to precisely control and configure these devices. One of these, self-configuration, deals with the automated synthesis of optical circuit configurations -even in presence of parasitic effects such as nonuniform losses, optical and electrical crosstalk- without any need for prior knowledge about hardware state. There are occasions, though, in which accessing to this information may be of use. Self-calibration and self-characterization tools allow us to perform a quick check to our photonic processor's status, allowing us to retrieve useful pieces of information such as the electrical current needed to supply to each phase actuator to change its corresponding PUC state arbitrarily or the insertion loss of every unit cell and optical interconnection surrounding the structure. These mechanisms not only allow us to quickly identify any malfunctioning PUCs or chip areas in our design, but also reveal another alternative to program photonic circuits in our design from current pre-sets. These strategies constitute a gigantic step to unleash all the potential of these devices. They provide solutions to handle with hundreds of variables and simultaneously manage multiple configuration actions, one of the main limitations that prevent this technology to scale up and become disruptive in the years to come.López Hernández, A. (2023). Multipurpose Programmable Integrated Photonics: Principles and Applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/19686

Surface Plasmon Polaritonic Crystals for Applications in Optical communications

The integration and reduction in the photonic device sizes are essential for the development of applications in short-range interconnects and optical signal processing. Surface plasmon polaritonic crystals (SPPCs) can allow the manipulation of optical information in the microscale level, by coupling photons with collective electron oscillations at a metal–dielectric interface. This thesis investigates, both numerically and experimentally, the excitation and propagation of the surface plasmon polaritonic (SPP) modes on finite-size SPPCs, their dependence on the nanostructured geometry and the potential applications in implementing different device functions including SPP-beam shaping, such as focusing and splitting, and wavelength/polarisation demultiplexing. By controlling the SPPC geometry and the excitation beam parameters, directional control of propagating plasmonic modes properties, such as the beam direction, focusing power and beam width, can be achieved. The wavelength-dependent SPP signal spatial separation, due to coupling to the several eigenmodes, and the reduction of the cross-talk by combining polarisation and wavelength modulation have also been shown. In addition, a compact 4-level polarisation discriminator based on a planar, microscale-scale SPPC was developed as part of the research. Its capability to spatially separate linearly polarised signals with azimuth angles 0o , 45o , 90o and 135o , and define the S1 and S2 stokes parameters of any elliptical polarisation state was demonstrated and experimentally tested. The concept was extended to propose a fibre-coupled polarimeter, able to identify the three Stokes vectors parameters, based on the combination of the SPPC with a high -birefringence fibre. The use of SPPCs for the implementation and miniaturisation of key optical communication functionalities, in-plane plasmonic beam manipulation and polarisation/wavelength dependent SPP beam propagation, demonstrated in this work can be important for the development of novel integrated nanophotonic functionalities for subwavelength management of optical signals and the design of a new family of compact devices for optical communication applications

Phase front accelerator effects in optical branching waveguides.

by Chan Hau Ping, Andy.Thesis (Ph.D.)--Chinese University of Hong Kong, 1991.Includes bibliographies.AcknowledgementAbstractChapter 1. --- Introduction --- p.1-1Chapter 1.1 --- Introduction and State-of-the-Art --- p.1-1Chapter 1.2 --- Application of Branching Waveguides Structure --- p.1-7Chapter 1.2.1 --- Mach-Zehnder interferometer --- p.1-8Chapter 1.2.2 --- Branching waveguide switch --- p.1-11Chapter 1.2.3 --- TE-TM mode splitter --- p.1-16Chapter 1.2.4 --- Wavelength multi/demultiplexer --- p.1-18Chapter 1.2.5 --- Temperature sensors --- p.1-20Chapter 1.2.6 --- Pressure sensors --- p.1-21Chapter 1.2.7 --- Summary --- p.1-22Chapter 1.3 --- Y-Branch Waveguide --- p.1-23Chapter 1.3.1 --- General structure --- p.1-23Chapter 1.3.2 --- Characteristic of Y-branch waveguides --- p.1-25Chapter 1.4 --- Summary --- p.1-31Chapter 1.5 --- References --- p.1-32Chapter 2. --- Phase Front Accelerator Design (PFA) --- p.2-1Chapter 2.1 --- Introduction --- p.2-1Chapter 2.2 --- PFA design in abrupt bend structure --- p.2-4Chapter 2.3 --- PFA design in symmetric Y-junction --- p.2-8Chapter 2.4 --- Advantages of using PFA design --- p.2-10Chapter 2.5 --- Summary --- p.2-13Chapter 2.6 --- References --- p.2-15Chapter 3. --- Beam Propagation Method (BPM) --- p.3-1Chapter 3.1 --- Introduction --- p.3-1Chapter 3.1.1 --- Effective index method --- p.3-1Chapter 3.1.2 --- Finite element method --- p.3-2Chapter 3.1.3 --- Beam propagation method --- p.3-2Chapter 3.2 --- Theory of Beam Propagation Method --- p.3-5Chapter 3.2.1 --- Helmholtz beam propagation method --- p.3-5Chapter 3.2.2 --- Fresnel beam propagation method --- p.3-7Chapter 3.3 --- Simulation Consideration --- p.3-11Chapter 3.4 --- Conclusion --- p.3-14Chapter 3.5 --- References --- p.3-14Chapter 4. --- Operation Mechanism of Phase Front Accelerator --- p.4-1Chapter 4.1 --- Introduction --- p.4-1Chapter 4.2 --- Structural Effect and Accelerator Effect --- p.4-1Chapter 4.3 --- Analysis and Discussion --- p.4-4Chapter 4.4 --- Figure of Merit in using PFA Design --- p.4-6Chapter 4.5 --- Conclusion --- p.4-14Chapter 4.6 --- References --- p.4-14Chapter 5. --- A 1x3 Optical Power Divider using PFA Design --- p.5-1Chapter 5.1 --- Introduction --- p.5-1Chapter 5.2 --- Design Structure --- p.5-3Chapter 5.3 --- Results and Discussion --- p.5-4Chapter 5.4 --- Conclusion --- p.5-7Chapter 5.5 --- References --- p.5-7Chapter 6. --- An Integrated Optical Beam Splitter using PFA Design --- p.6-1Chapter 6.1 --- Introduction --- p.6-1Chapter 6.2 --- Design Structure --- p.6-3Chapter 6.3 --- Illustrations --- p.6-7Chapter 6.4 --- Analysis and Discussion --- p.6-12Chapter 6.5 --- Conclusion --- p.6-19Chapter 6.6 --- References --- p.6-19Chapter 7. --- PFA Effects in Asymmetric Branching Waveguides --- p.7-1Chapter 7.1 --- Introduction --- p.7-1Chapter 7.2 --- Design Structure --- p.7-4Chapter 7.3 --- Analysis and Discussion --- p.7-4Chapter 7.3.1 --- PFA effects on mode conversion in Y-branch waveguide --- p.7-11Chapter 7.3.2 --- A 3dB coupler in asymmetric Y-branch waveguide --- p.7-16Chapter 7.4 --- Conclusion --- p.7-19Chapter 7.5 --- References --- p.7-21Chapter 8. --- Fabrication of Titanium In-diffused Waveguide in LiNb03 --- p.8-1Chapter 8.1 --- Introduction --- p.8-1Chapter 8.2 --- Substrate Crystal Cleaning --- p.8-2Chapter 8.3 --- Resist Coating --- p.8-3Chapter 8.4 --- Photolithography --- p.8-6Chapter 8.5 --- Lift-off Technique --- p.8-6Chapter 8.6 --- Titanium In-diffusion --- p.8-9Chapter 8.7 --- Lapping and Polishing --- p.8-12Chapter 8.8 --- Conclusion --- p.8-14Chapter 8.9 --- References --- p.8-14Chapter 9. --- Truncated Structural Y-Branch Design --- p.9-1Chapter 9.1 --- Introduction --- p.9-1Chapter 9.2 --- Theoretical Analysis --- p.9-5Chapter 9.3 --- Fabrication of Waveguides --- p.9-6Chapter 9.4 --- Experimental Set-up and Measurement --- p.9-11Chapter 9.5 --- Experimental Results and Discussion --- p.9-14Chapter 9.6 --- Conclusion --- p.9-18Chapter 9.7 --- References --- p.9-19Chapter 10. --- Conclusion --- p.10-1Contributions - list of publications --- p.A-

Advances in the Spectral Index method for the analysis of photonic integrated circuits

The prolific rate at which advances in photonics have been made in recent years has increased the need for accurate and efficient computer aided design tools. New device technologies and material systems mean the designer is faced with many more degrees of freedom with which to optimise a design. Because of this versatile techniques that yield results accurately and quickly are foremost in the designers mind. Throughout this work a well proven technique, the Spectral Index (SI) method is extended and generalised to a wide variety design situations of practical importance. The design of a novel Silicon Germanium based device was used to prove the suitability of an iterative design methodology in developing and optimising practical waveguiding components. The novel development of the SI method for the accurate analysis of waveguide losses is then presented further extending its suitability to the analysis and design of rectangular rib waveguides. Following this the generalisation of the SI method to structures of non-rectangular cross-section is presented allowing for the analysis of a wider range of optical rib waveguides. A novel implementation of the SI method is then developed for the analysis of the whispering gallery class of resonant modes supported by cylindrical dielectric disc and ring structures, allowing for the characterisation of the optical properties of this important class of devices. A 3D circuit analysis technique based upon a robust implementation of the SI method in its complex form is developed that allows for the characterisation of any waveguide system that may be represented by a number of discrete waveguide components. Finally the SI method is generalised to the full 3D exact analysis of optical waveguiding structure

Tunable Silicon integrated photonics based on functional materials

This thesis is concerned with the design, fabrication, testing and development of tunable silicon photonic integrated circuits based on functional materials. This tunability is achieved by integrating liquid crystals, 2D materials and chalcogenide phase-change materials with silicon and silicon nitride integrated circuits. Switching the functional materials between their various states results in dramatic changes in the optical properties, with consequent changes in the optical response of the individual devices. Furthermore, such changes are volatile or non-volatile depending on the materials.Engineering and Physical Sciences Research Council (EPSRC

Next Generation Silicon Photonic Transceiver: From Device Innovation to System Analysis

Silicon photonics is recognized as a disruptive technology that has the potential to reshape many application areas, for example, data center communication, telecommunications, high-performance computing, and sensing. The key capability that silicon photonics offers is to leverage CMOS-style design, fabrication, and test infrastructure to build compact, energy-efficient, and high-performance integrated photonic systems-on- chip at low cost. As the need to squeeze more data into a given bandwidth and a given footprint increases, silicon photonics becomes more and more promising. This work develops and demonstrates novel devices, methodologies, and architectures to resolve the challenges facing the next-generation silicon photonic transceivers. The first part of this thesis focuses on the topology optimization of passive silicon photonic devices. Specifically, a novel device optimization methodology - particle swarm optimization in conjunction with 3D finite-difference time-domain (FDTD), has been proposed and proven to be an effective way to design a wide range of passive silicon photonic devices. We demonstrate a polarization rotator and a 90◦ optical hybrid for polarization-diversity and phase-diversity communications - two important schemes to increase the communication capacity by increasing the spectral efficiency. The second part of this thesis focuses on the design and characterization of the next- generation silicon photonic transceivers. We demonstrate a polarization-insensitive WDM receiver with an aggregate data rate of 160 Gb/s. This receiver adopts a novel architecture which effectively reduces the polarization-dependent loss. In addition, we demonstrate a III-V/silicon hybrid external cavity laser with a tuning range larger than 60 nm in the C-band on a silicon-on-insulator platform. A III-V semiconductor gain chip is hybridized into the silicon chip by edge-coupling to the silicon chip. The demonstrated packaging method requires only passive alignment and is thus suitable for high-volume production. We also demonstrate all silicon-photonics-based transmission of 34 Gbaud (272 Gb/s) dual-polarization 16-QAM using our integrated laser and silicon photonic coherent transceiver. The results show no additional penalty compared to commercially available narrow linewidth tunable lasers. The last part of this thesis focuses on the chip-scale optical interconnect and presents two different types of reconfigurable memory interconnects for multi-core many-memory computing systems. These reconfigurable interconnects can effectively alleviate the memory access issues, such as non-uniform memory access, and Network-on-Chip (NoC) hot-spots that plague the many-memory computing systems by dynamically directing the available memory bandwidth to the required memory interface

Advances in the Spectral Index method for the analysis of photonic integrated circuits

The prolific rate at which advances in photonics have been made in recent years has increased the need for accurate and efficient computer aided design tools. New device technologies and material systems mean the designer is faced with many more degrees of freedom with which to optimise a design. Because of this versatile techniques that yield results accurately and quickly are foremost in the designers mind. Throughout this work a well proven technique, the Spectral Index (SI) method is extended and generalised to a wide variety design situations of practical importance. The design of a novel Silicon Germanium based device was used to prove the suitability of an iterative design methodology in developing and optimising practical waveguiding components. The novel development of the SI method for the accurate analysis of waveguide losses is then presented further extending its suitability to the analysis and design of rectangular rib waveguides. Following this the generalisation of the SI method to structures of non-rectangular cross-section is presented allowing for the analysis of a wider range of optical rib waveguides. A novel implementation of the SI method is then developed for the analysis of the whispering gallery class of resonant modes supported by cylindrical dielectric disc and ring structures, allowing for the characterisation of the optical properties of this important class of devices. A 3D circuit analysis technique based upon a robust implementation of the SI method in its complex form is developed that allows for the characterisation of any waveguide system that may be represented by a number of discrete waveguide components. Finally the SI method is generalised to the full 3D exact analysis of optical waveguiding structure