Dissertations / Theses on the topic 'Silicon photonic chip'

Microelectronics has enjoyed great success in the past century. As the technology node progresses, the complementary metal-oxide-semiconductor scaling has already reached a wall, and serious challenges in high-bandwidth interconnects and fast-speed signal processing arise. The incorporation of photonics to microelectronics provides potential solutions. The theme of this thesis is focused on the novel applications of travelling-wave microresonators such as microdisks and microrings for the on-chip optical interconnects and signal processing. Challenges arising from these applications including theoretical and experimental ones are addressed. On the theoretical aspect, a modified version of coupled mode theory is offered for the TM-polarization in high index contrast material systems. Through numerical comparisons, it is shown that our modified coupled mode theory is more accurate than all the existing ones. The coupling-induced phase responses are also studied, which is of critical importance to coupled-resonator structures. Different coupling structures are studied by a customized numerical code, revealing that the phase response of symmetric couplers with the symmetry about the wave propagating direction can be simply estimated while the one of asymmetric couplers is more complicated. Mode splitting and scattering loss, which are two important features commonly observed in the spectrum of high-Q microresonators, are also investigated. Our review of the existing analytical approaches shows that they have only achieved partial success. Especially, different models have been proposed for several distinct regimes and cannot be reconciled. In this thesis, a unified approach is developed for the general case to achieve a complete understanding of these two effects. On the experimental aspect, we first develop a new fabrication recipe with a focus on the accurate dimensional control and low-loss performance. HSQ is employed as the electron-beam resist, and the lithography and plasma etching steps are both optimized to achieve vertical and smooth sidewalls. A third-order temperature-insensitive coupled-resonator filter is designed and demonstrated in the silicon-on-insulator (SOI) platform, which serves as a critical building block element in terabit/s on-chip networks. Two design challenges, i.e., a broadband flat-band response and a temperature-insensitive design, are coherently addressed by employing the redundant bandwidth of the filter channel caused by the dispersion as thermal guard band. As a result, the filter can accommodate 21 WDM channels with a data rate up to 100 gigabit/s per wavelength channel, while providing a sufficient thermal guard band to tolerate more than ±15°C temperature fluctuations in the on-chip environment. In this thesis, high-Q microdisk resonators are also proposed to be used as low-loss delay lines for narrowband filters. Pulley coupling scheme is used to selectively couple to one of the radial modes of the microdisk and also to achieve a strong coupling. A first-order tunable narrowband filter based on the microdisk-based delay line is experimentally demonstrated in an SOI platform, which shows a tunable bandwidth from 4.1 GHz to 0.47 GHz with an overall size of 0.05 mm². Finally, to address the challenges for the resonator-based delay lines encountered in the SOI platform, we propose to vertically integrate silicon nitride to the SOI platform, which can potentially have significantly lower propagation loss and higher power handling capability. High-Q silicon nitride microresonators are demonstrated; especially, microresonators with a 16 million intrinsic Q and a moderate size of 240 µm radius are realized, which is one order of magnitude improvement compared to what can be achieved in the SOI platform using the same fabrication technology. We have also successfully grown silicon nitride on top of SOI and a good coupling has been achieved between the silicon nitride and the silicon layers.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.
"June 2004."
Includes bibliographical references (leaves 170-180).
This thesis focuses on integrated silicon based photonic structures, photonic band gap (PBG) and quasi-photonic band gap (QPX) structures, which are based on high refractive index contrast dielectric layers and CMOS compatibility. We developed a new type of silicon waveguide - Photonic Crystal (PC) cladding waveguide is studied based on PBG principle. The refractive index in the new PC cladding waveguide core therefore has a large flexibility. Low index core (e.g. SiO2) or hollow core waveguide can be realized with our PC cladding waveguide structure. The fabrication of the waveguide is compatible to CMOS process. To demonstrate the PBG guiding mechanism, we utilized prism coupling to the Asymmetric PC cladding waveguide and the effective index of the propagation mode is measured directly. The measured effective mode index is less than both Si and Si3N4 cladding layers, which is clear demonstration of the photonic band gap guiding principle. We also fabricated and measured the PC cladding channel waveguide. Potential applications include high power transmission, low dispersion, thin cladding thickness and nonlinear properties engineering. Secondly, we developed a Si-based multi-channel optical filter with tunability, which is based on omnidirectional reflecting photonic band gap structure with a relatively large air gap defect. Using only one device, multi channel filter with tunability around two telecom wavelength 1.55[mu]m and 1.3[mu]m by electrostatic force is realized. Four widely spaced resonant modes within the photonic band gap are observed, which is in good agreement with numerical simulations.
(cont.) The whole process is compatible with current microelectronics process technology. There are several potential applications of this technology in wavelength division multiplexing (WDM) devices. Thirdly, to further extend the photonic crystal idea, we studied the quasi-photonic crystal structures and their properties, especially for the fractal photonic band gap properties and the transparent resonant transmission states. A-periodic Si/SiO2 Thue-Morse (T-M) multilayer structures have been fabricated, for the first time, to investigate both the scaling properties and the omnidirectional reflectance at the fundamental optical band-gap. Variable angle reflectance data have experimentally demonstrated a large reflectance band-gap in the optical spectrum of a T-M quasicrystal, in agreement with transfer matrix simulations. The physical origin of the T-M omnidirectional band-gap has been explained as a result of periodic spatial correlations in the complex T-M structure. The unprecedented degree of structural flexibility of T-M systems can provide an attractive alternative to photonic crystals for the fabrication of photonic devices.
by Yasha Yi.
Ph.D.

Les futurs calculateurs de haute performance (HPC) devront faire face à deux défis majeurs : la densité de la bande passante d'interconnexion et les problématiques de consommation d'énergie. La photonique silicium est aujourd’hui perçue comme une solution solide pour aborder ces questions, tant du fait de ses performances que de sa viabilité économique en raison de sa compatibilité directe avec la microélectronique CMOS. Actuellement, une tendance de fond conduit à remplacer les interconnexions métalliques par des liens optiques ; cette évolution a été initiée sur des liaisons grandes distances mais atteint actuellement le niveau des liaisons entre cartes électroniques et pourrait conduire à moyen terme à l’intégration de liens optiques au sein mêmes des circuits intégrés électroniques. La prochaine étape est en effet envisagée pour l'interconnexion des processeurs au sein de puces multi-cœurs en positionnant les liens photoniques sur un même support de silicium (« interposer »). Plusieurs travaux ont démontré la possibilité d'intégrer tous les éléments nécessaires pour la réalisation de liaisons optiques sur un substrat de silicium ouvrant des perspectives de co-intégration optique et électronique très riches.Dans ce contexte, la première contribution de cette thèse est l'optimisation d'un lien de photonique de silicium en terme d'efficacité énergétique par bit (à minimiser). L'optimisation que nous avons conduite a pris en compte une modélisation de la consommation d'énergie pour le laser de la liaison, celle de l’étape dé-sérialisation des données, du résonateur en anneau considéré comme modulateur optique et des circuits de réception (« front-end ») et de décision. Les résultats ont montré que les principales contributions à la consommation de puissance au sein d’un lien optique sont la puissance consommée par le laser et les circuits d’alimentation du modulateur électro-optique. En considérant des paramètres de consommation extraits de simulations numériques et de travaux publiés dans des publications récentes, le débit optimal identifié se trouve dans la plage comprise entre 8 Gbits/seconde et 22 Gbits/seconde selon le nœud technologique CMOS utilisé (65nm à 28nm FD SOI). Il est également apparu qu’une diminution de la consommation de puissance statique du modulateur utilisé pourrait encore ramener ce débit optimal en-dessous de 8 Gbits/seconde.Afin de vérifier ces résultats, un circuit intégré récepteur de liaison optique a été conçu et fabriqué en se basant sur un débit de fonctionnement de 8 Gbits/seconde. Le récepteur utilise une technique d’entrelacement temporel destinée à réduire la vitesse d'horloge nécessaire et à éviter potentiellement l’étape de dé-sérialisation dédiée des informations
Future high performance computer (HPC) systems will face two major challenges: interconnection bandwidth density and power consumption. Silicon photonic technology has been proposed recently as a cost-effective solution to tackle these issues. Currently, copper interconnections are replaced by optical links at rack and board level in HPCs and data centers. The next step is the interconnection of multi-core processors, which are placed in the same package on silicon interposers, and define the basic building blocks of these computers. Several works have demonstrated the possibility of integrating all elements needed for the realization of short optical links on a silicon substrate.The first contribution of this thesis is the optimization of a silicon photonic link for highest energy efficiency in terms of energy per bit. The optimization provides energy consumption models for the laser, a de- and serialization stage, a ring resonator as modulator and supporting circuitry, a receiver front-end and a decision stage. The optimization shows that the main consumers in optical links is the power consumed by the laser and the modulator's supporting circuitry. Using consumption parameters either gathered by design and simulation or found in recent publications, the optimal bit rate is found in the range between 8 Gbps and 22 Gbps, depending on the used CMOS technology. Nevertheless, if the static power consumption of modulators is reduced it could decrease even below 8 Gbps.To apply the results from the optimization an optical link receiver was designed and fabricated. It is designed to run at a bit rate of 8 Gbps. The receiver uses time interleaving to reduce the needed clock speed and aleviate the need of a dedicated deserialization stage. The front-end was adapted for a wide dynamic input range. In order to take advantage of it, a fast mechanism is proposed to find the optimal threshold voltage to distinguish ones from zeros.Furthermore, optical clock channels are explored. Using silicon photonics a clock can be distributed to several processors with very low skew. This opens the possibility to clock all chips synchronously, relaxing the requirements for buffers that are needed within the communication channels. The thesis contributes to this research direction by presenting two novel optical clock receivers. Clock distribution inside chips is a major power consumer, with small adaptation the clock receivers could also be used inside on-chip clocking trees

La photonique au silicium est une technologie émergente considérée comme l'une des solutions clés pour les interconnexions sur puce de génération future, offrant plusieurs avantages potentiels tels qu'une faible latence de transmission et une bande passante élevée. Cependant, elle reste confrontée à des défis en matière d'efficacité énergétique. Différentes topologies, layout et architectures offrent diverses options d'interconnexion. Ceci conduit à une grande variation des pertes optiques, qui est l'un des facteurs prédominants dans la consommation d'énergie. De plus, les composants photoniques au silicium sont très sensibles aux variations de température. Sous une activité de puces donnée, ceci conduit à une réduction de l’efficacité des lasers et à une dérive des longueurs d'onde des composants optiques, ce qui entraîne un «Bit Error Ratio (BER)» plus élevé et réduit par conséquent l'efficacité énergétique des interconnexions optiques. Dans cette thèse, nous travaillons sur des méthodologies de conception pour les interconnexions photoniques sur silicium économes-en-énergie et prenant en compte la topologie / le layout, la variation thermique et l'architecture
Silicon photonics is an emerging technology considered as one of the key solutions for future generation on-chip interconnects, providing several prospective advantages such as low transmission latency and high bandwidth. However, it still encounters challenges in energy efficiency. Different topologies, physical layouts, and architectures provide various interconnect options for on-chip communication. This leads to a large variation in optical losses, which is one of the predominant factors in power consumption. In addition, silicon photonic devices are highly sensitive to temperature variation. Under a given chip activity, this leads to a lower laser efficiency and a drift of wavelengths of optical devices (on-chip lasers and microring resonators (MRs)), which in turn results in a higher Bit Error Ratio (BER) and consequently reduces the energy efficiency of optical interconnects. In this thesis, we work on design methodologies for energy-efficient silicon photonic interconnects on chip related to topology/layout, thermal variation, and architecture

Microcantilever arrays have been shown to be promising label-free nanomechanical sensing devices with high sensitivity. Two factors that affect the usefulness of microcantilevers in sensing scenarios are the sensitivity of the transduction method for measuring changes in microcantilever properties and the ability to create large compact arrays of microcantilevers. In this dissertation, we demonstrate that microcantilevers with an in-plane photonic transduction method are attractive because they maintain the sensitivity of the traditional laser beam reflection method while being scalable to simultaneous readout of large microcantilever arrays. First I demonstrate the integration of a compact waveguide splitter network with in-plane photonic microcantilevers which have amorphous silicon strip loading differential splitter and simultaneous microcantilever readout with an InGaAs line scan camera. A 16-microcantilever array is fabricated and measured. Use of a scaled differential signal yields reasonable correspondence of the signals from 7 surviving released microcantilevers in the array. The average sensitivity is 0.23 µm-1. To improve the sensitivity and consistency, and reduce fabrication difficulties, a new differential splitter design with 4 µm long double-step multimode rib waveguide is introduced. Furthermore, a modified fabrication process is employed to enhance the performance of the device. A new 16-microcanitiler array is designed and fabricated. The sensitivity of a measured 16-microcantilever array is improved to approximately 1 µm-1, which is comparable to the best reported for the laser reflection read out method. Moreover, most of the microcantilevers show excellent uniformity. To demonstrate large scale microcantilever arrays with simultaneous readout using the in-plane photonic transduction method, a 64-microcantilver array is designed, fabricated and measured. Measurement results show that excellent signal uniformiy is obtained for the scaled differential signal of 56 measured microcantilevers in a 64-array. The average sensitivity of the microcantilevers is 0.7 µm-1, and matches simulation results very well.

The objective of this work is to develop essential building blocks for the lab-on-a-chip optical sensing systems with high performance. In this study, the silicon-on-insulator (SOI) platform is chosen because of its compatibility with the mature microelectronics industry for the great potential in terms of powerful data processing and massive production. Despite the impressing progress in optical sensors based on the silicon photonic technologies, two constant challenges are larger sensitivity and better selectivity. To address the first issue, we incorporate porous materials to the silicon photonics platform. Two porous materials are investigated: porous silicon and porous titania. The demonstrated travelling-wave resonators with the magnesiothermically reacted porous silicon cladding have shown significant enhancement in the sensitivity. The process is then further optimized by replacing the thermal oxide with a flowable oxide for the magnesiothermic reduction. A different approach of making porous silicon using porous anodized alumina membrane leads to better flexibility in controlling the pore size and porosity. Porous titania is successfully integrated with silicon nitride resonators. To improve the selectivity, an array of integrated optical sensors are coated with different polymers, such that each incoming gas analyte has its own signature in the collective response matrix. A multiplexed gas sensor with four polymers has been demonstrated. It also includes on chip references compensating for the adverse environmental effects. On chip spectral analysis is also very critical for lab-on-a-chip sensing systems. For that matter, based on an array of microdonut resonators, we demonstrate an 81 channel microspectrometer. The demonstrated spectrometer leads to a high spectral resolution of 0.6 nm, and a large operating bandwidth of ~ 50 nm.

[EN] Optical technologies are the backbone of modern communication systems providing high-speed access to the Internet, efficient inter and intra-data center interconnects and are expending towards growing research fields and new markets such as satel- lite communications, LIDARs (Laser Imaging Detection and Ranging) applications, Neuromorphic computing, and programable photonic circuits, to name a few. Be- cause of its maturity and low-cost, silicon photonics is being leveraged to allow these new technologies to reach their full potential.As a result, there is a strong need for innovative, high-speed and energy-efficient photonic integrated building blocks on the silicon platform to increase the readiness of silicon photonic integrated circuits. The work developed and presented in this thesis is focused on the design and char- acterization of advanced passive and active devices, for photonic integrated circuits. The thesis consists of three main chapters as well as a motivation and concluding sections exposing the rationale and the accomplishments of this work. Chapter one describes the design and characterization of an electro-optical Mach-Zehnder mod- ulator embedded in highly efficient vertical pn junction exploiting the free-carrier dispersion effect in the O-band.. Chapter two is devoted to the design and charac- terization of a novel geometry of asymmetrical multimode interference device and its implementation in a Mach-Zehnder modulator. Chapter three is dedicated to the design and characterization of innovative 1-dimensional photonic crystal designs for slow- lightmodulation applications. An extensive analysis of the main trade-off arising from the use of slow light is presented.
[ES] Las tecnologías ópticas son el eje vertebrador de los sistemas de comunicación mod- ernos que proporcionan acceso de alta velocidad a la Internet, interconexiones efi- cientes entre centros de datos y dentro de ellos. Además, se están expandiendo hacia campos de investigación crecientes y nuevos mercados como son las aplicaciones de comunicaciones por satélite, los LIDAR (Laser Imaging Detection and Ranging), la computación neuromórfica y los circuitos fotónicos programables, por nombrar algunos. La fotónica de silicio está considerada y aceptada ampliamente como una de las tecnologías clave para que dichas aplicaciones puedan desarrollarse. Como resultado, hay una fuerte necesidad de estructuras fotónicas básicas integradas que sean innovadoras, que soporten altas velocidades de transmisión y que sean más eficientes en términos de consumo de potencia, a fin de aumentar la capacidad de los circuitos integrados fotónicos de silicio. El trabajo desarrollado y presentado en esta tesis se centra en el diseño y la car- acterización de dispositivos avanzados pasivos y activos, para circuitos fotónicos integrados. La tesis consta de tres capítulos principales, así como de sendas sec- ciones de motivación y conclusiones que exponen los fundamentos y los logros de este trabajo. El capítulo uno describe el diseño y la caracterización de un modulador electro-óptico Mach-Zehnder incorporado en una unión pn vertical altamente eficien- ciente que explota el efecto de dispersión de plasma en banda O. El capítulo dos está dedicado al diseño y caracterización de una nueva geometría de dispositivo de interferencia multimodo asimétrico y su aplicación en un modulador Mach-Zehnder. El capítulo tres está dedicado al diseño y caracterización de innovadores cristales fotónicos unidimensionales para aplicaciones de modulación con luz lenta. Se pre- senta un amplio análisis de los principales retos derivados del uso de la misma.
[CA] Les tecnologies òptiques són l'eix vertebrador d'aquells sistemes de comunicació moderns que proporcionen accés d'alta velocitat a la Internet, així com intercon- nexions eficients inter i entre centres de dades. A més a més, s'estan expandint cap a camps d'investigació creixents i nous mercats com són les aplicacions de co- municacions per satèl·lit, els LIDAR (Laser Imaging Detection and Ranging), la computació neuromòrfica i els circuits fotònics programables, entre d'altres. La fotònica de silici és considerada i acceptada àmpliament com una de les tecnologies clau i necessàries perquè aquestes aplicacions puguen desenvolupar-se. Per aquest motiu, es fa necessària l'existència d'estructures fotòniques bàsiques integrades que siguen innovadores, que suporten altes velocitats de transmissió i que siguen més eficients en termes de consum de potència, a fi d'augmentar la capacitat dels cir- cuits integrats fotònics de silici. El treball desenvolupat i presentat en aquesta tesi se centra en el disseny i la caracterització de dispositius avançats passius i actius, per a circuits fotònics integrats. La tesi consta de tres capítols principals, així com d'una secció de motivació i una altra de conclusions que exposen els fonaments i els assoliments d'aquest treball. El capítol u descriu el disseny i la caracterització d'un modulador electro-òptic Mach-Zehnder incorporat en una unió pn vertical d'alta efi- ciència que explota l'efecte de dispersió de plasma en la banda O. El capítol dos està dedicat al disseny i caracterització d'una nova geometria de dispositiu d'interferència multimode asimètric així com a la seua aplicació en un modulador Mach-Zehnder. El capítol tres està dedicat al disseny i caracterització d'innovadors cristalls fotònics unidimensionals per a aplicacions de modulació amb llum lenta. S'inclou també una anàlisi detallada dels principals reptes derivats de l'ús d'aquest tipus de llum.
I want to thank you the Generelitat Valenciana and the European Project L3MATRIX for the funding, without them my doctorate would not taken place.
Zanzi, A. (2020). Passive and active silicon photonics devices at TLC telecommunication wavelengths for on-chip optical interconnects [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149377
TESIS

Cette thèse est une contribution à la modélisation et à l'étude expérimentale de cavités à cristaux photoniques à fente développées en vue d’un intégration hybride de matériaux actifs sur silicium. Parmi les travaux de conception, nous avons d'abord utilisé la méthodes des ondes planes et la méthode des différences finies (FDTD) pour concevoir une série de cavités SOI à hétérostructures, mécaniquement robustes, infiltrées par des liquides d’indices (n environ 1,5), présentant des longueurs d'onde de résonance dans la gamme des télécommunications (1,3 μm - 1,6 μm), des facteurs de qualité de plusieurs dizaines de milliers, et des volumes modaux proches de 0,03 (lambda/n)3. Nous avons ensuite étudié analytiquement et numériquement le couplage entre une cavité à cristaux photoniques à fente et un guide d'onde à fente par la théorie des modes couplés, complétée par des simulations FDTD, qui ont permis de confirmer la possibilité d'exciter efficacement les modes de fente des cavités à partir d'un guide externe. Enfin, nous avons étudié numériquement et semi-analytiquement des géométries de molécules photoniques constituées de deux cavités à cristaux photoniques à fentes couplées, dont l’écart fréquentiel entre les supermodes a pu être ajusté en amplitude et en signe. Nous avons utilisé une méthode perturbative (« Tight binding ») pour estimer les distributions spatiales des modes des molécules photoniques et prédire leurs fréquences dans plusieurs configurations de cavités à cristaux photoniques à fentes couplées.Ce travail exploratoire a été complété par une partie expérimentale qui a porté sur l'étude d'une famille de cavités de hétérostructure à cristaux photoniques à fente. Les cavités à cœur creux fabriquées ont montré des facteurs de qualité (Q) de plusieurs dizaines de milliers, associés à des volumes modaux de l’ordre de V=0,03 (λ/n)^3 après infiltration de la fente et des trous des structures par des liquides d'indice de réfraction proches de 1,46. Des facteurs Q/V supérieurs à 600 000 et atteignant 1 000 000 dans le meilleur des cas (vers lambda=1,3µm) ont ainsi été observés. Cette phase expérimentale préliminaire a donné ensuite lieu à deux types de développements.Tout d'abord, les propriétés des cavités à cristaux photoniques à fentes ont été étudiées pour des applications en détection d'indice en volume, et testées en utilisant différents liquides d'indice de réfraction compris entre 1,345 à 1,545. Les résonateurs étudiés ont présenté des sensibilités de ~ 235 nm / RIU et des facteur de mérite de détection d'indice de l’ordre de 3700, à l’état de l’art pour des résonateurs silicium intégrés à cœur creux.Dans une autre direction, le potentiel des résonateurs diélectriques à fente a été exploré en vue d’une intégration des matériaux actifs sur silicium. Un polymère dopé aux nanotubes de carbone semiconducteurs a été déposé comme matériau de couverture en vue d’étudier le renforcement de la photoluminescence (PL) des nano-émetteurs sous pompage optique vertical à lambda=740nm. Les expériences conduites ont permis de corréler le renforcement de la PL des nanotubes avec les modes de résonance des cavités et de démontrer le couplage partiel de cette PL vers des guides SOI longs de plusieurs millimètres (collection par la tranche vers lambda=1.3µm), apportant une preuve de principe d’une possible intégration des nanotubes émetteurs en photonique sur silicium
This Ph.D. work is a contribution to the modeling and the experimental study of slot photonic crystal cavities for hybrid on-silicon integration. Among the design works, we first have used plane the wave expansion and finite-difference time-domain methods to design a series of mechanically robust (non-free membrane) SOI slot photonic crystal heterostructure cavities with resonance wavelengths in the telecommunication range, i.e. from 1.3 µm – 1.6 µm, with Q-factors of around several tens of thousands and mode volumes around 0.03(lambda/n)^3 after being infiltrated by cladding materials with typical index values around 1.5. We have then analytically and numerically studied the coupling between a slot photonic crystal cavity and a slot photonic crystal waveguide by using the coupled mode theory and FDTD simulation. Then we confirmed the ability to excite the cavity slot modes from a waveguide by using FDTD simulation. Finally, as a preliminary step towards the use of several coupled slotted cavities for future hybrid integration schemes, we have numerically and semi-analytically investigated photonic molecules made of two coupled slot photonic crystal cavities providing two different supermodes (bonding and antibonding ones) with controllable wavelength splitting. We successfully employed the tight-binding (TB) approach, which relies on the overlap of the two tightly confined cavity electric fields, to predict the supermodes frequencies and spatial distributions in several coupled slot photonic crystal cavity configurations.This exploratory work was supplemented by an experimental part, which focused on the investigation of a family of slot photonic crystal heterostructure cavities. The fabricated silicon on insulator hollow core cavities showed quality factors of several tens of thousands, i.e. from 18,000 to 31,000 and mode volume V of ~0.03(λ/n)3 after being infiltrated with liquids of ~1.46 refractive index, yielding Q/V ratio larger than 600,000, and reaching 1,000,000 in the best case (at λ ≈ 1.3 μm).This preliminary experimental stage gave rise to two types of additional developments.Firstly, the properties of the studied slot photonic crystal cavities have been investigated for index sensing applications by using different liquids with refractive index values ranging from 1.345 to 1.545. The considered photonic crystal resonators have demonstrated quality factors of several tens of thousands with sensitivities of ~235 nm/RIU and index sensing FOMs around 3,700, i.e. at the state of the art considering hollow core silicon integrated resonators.Secondly, in the view of the integration of active materials on silicon, the potential of these hollow core nanoresonators has been considered to enhance the photo-luminescence (PL) of semiconductor single-walled carbon nanotubes (SWNTs) integrated in thin films deposited on top of silicon. We have brought the first experimental demonstration of SWNTs PL collection (around lambda=1.28 µm) under vertical pumping at short wavelength (lambda=740 nm) from a slotted resonator into millimeter long integrated silicon waveguides, providing a first proof-of-concept step towards nanotube/Si-PhC integration as an active photonic platform. The reported works demonstrate the feasibility of integrating telecommunication wavelength nanotube emitters in silicon photonics as well as emphasize the role of slot photonic crystal cavities for on-chip hybrid integration

Les travaux portent sur les multiplexeurs optiques fonctionnant à mi-IR pour la source à large bande dans l'application de détection de gaz. Deux configurations ont été étudiées: réseau de guides d'onde (AWG) et réseau concave planaire (PCG). Premièrement, le principe du fonctionnement a été compris afin de développer une solution analytique pour le champ de sortie en utilisant une approximation gaussienne du champ et de l'optique de Fourier. Ensuite, un outil de simulation semi-analytique de la réponse spectrale pour les deux configurations de multiplexeur a été développé dans MATLAB. La distribution normale des erreurs de phase a été introduite dans le modèle semi-analytique AWG, ce qui nous a permis d'étudier la corrélation entre l'écart-type des erreurs de phase et le niveau de diaphonie de la réponse spectrale AWG. AWG à 5,65 μm a été fabriqué à partir de la technologie SiGe / Si à l'aide de l'outil MATLAB pour le calcul des paramètres de conception et de l'outil P.Labeye pour le calcul de la géométrie AWG. Les dispositifs avec des paramètres légèrement variables ont été caractérisés: AWG1 avec guides d'ondes de 4,6 μm et MMI de 9 μm; AWG2 avec guides d'ondes de 4,6 μm et MMI de 11 μm; AWG3 avec guides d'ondes de 4,8 μm et MMI de 9 μm. Des mesures des dispositifs sur la puce 36 (centre de la plaquette) et sur la puce 32 (côté de la plaquette) ont été effectuées et analysées. Les mesures de température de AWG2 et AWG3 (puce 32 et puce 36) aux points cinq points de température ont montré une dépendance linéaire du déplacement spectral avec la température qui a une bonne corrélation avec les prédictions de simulation
The work focuses on optical multiplexers operating in mid-IR for broadband source in gas sensing application. Two configurations were studies – arrayed waveguide grating (AWG) and planar concave grating (PCG). First, principle of operation was understood in order to develop analytical solution for output field using Gaussian approximation of the field and Fourier Optics. Then, semi-analytical simulation tool of the spectral response for both multiplexer configurations was developed in MATLAB. Normal distribution of phase errors was introduced to semi-analytical AWG model, which allowed us to study the correlation between standard deviation of phase errors and the level of crosstalk of AWG spectral response. AWG at 5.65 µm was fabricated based on SiGe/Si technology using the MATLAB tool for design parameters calculation and P.Labeye’s tool for AWG geometry calculation. Devices with slightly varying parameters were characterized: AWG1 with 4.6 µm waveguides and 9µm MMI; AWG2 with 4.6 µm waveguides and 11µm MMI; AWG3 with 4.8 µm waveguides and 9µm MMI. Measurements of devices on chip 36 (center of the wafer) and chip 32 (side of the wafer) were performed and analyzed. Temperature measurements of AWG2 and AWG3 (chip 32 and chip 36) at points five temperature points showed linear dependence of spectral shift with the temperature which has a good correlation with simulation predictions

We investigate the properties of integrated dielectric filters for the purposes of on-chip routing of photons. We started with the use of high quality factor tunable photonic crystal nanobeam cavities and moving on to examine a new class of reflection based reverse designed filters that maintain the footprint of a waveguide while allowing for arbitrary amplitude and phase response.
Engineering and Applied Sciences

Esta tesis trata de resolver el problema de la interconexión (acoplo) entre un circuito integrado fotónico de silicio (chip) y el mundo exterior, es decir una fibra óptica. Se trata de uno de los temas más importantes a los que hoy en día se enfrenta la comunidad científica en óptica integrada de silicio. A pesar de que pueden realizarse circuitos integrados fotónicos de silicio de muy alta calidad utilizando herramientas estándar de fabricación CMOS, la interfaz con la fibra óptica sigue siendo la fuente más importante de pérdidas, debido a la gran diferencia en el tamaño entre los modos de propagación de la fibra y de las guías de los circuitos integrados fotónicos. Abordar el problema es, por lo tanto, muy importante para poder utilizar los circuitos integrados fotónicos de silicio en una aplicación práctica. Objetivos: El propósito de este trabajo es hacer frente a este problema en la interfaz del acoplamiento fibra-chip, con énfasis en el ensamblado o empaquetado final. Por lo tanto, los objetivos principales son: 1) estudio, modelado y optimización de diseños de diferentes técnicas eficientes de acoplamiento entre fibras ópticas y circuitos integrados fotónicos de silicio, 2) fabricación y demostración experimental de los diseños obtenidos, 3) ensamblado y empaquetado de algunos de los prototipos de acoplamiento fabricados. Metodología: Este trabajo se desarrolla a lo largo de dos líneas de investigación, en conformidad con las dos principales estrategias de acoplamiento que pueden encontrarse en la literatura, concretamente, estructuras de acoplamiento tipo "grating" (la fibra acopla verticalmente sobre la superficie de circuito), y estructuras del tipo ¿inverted taper¿ (la fibra acopla horizontalmente por el extremo de circuito). Resultados: tanto en el caso de estructuras tipo "grating" como en el caso de estructuras "inverted taper", son importantes los avances conseguidos sobre el estado del arte. En lo que respecta al "grating", se ha demostrado dos tipos de estructuras. Por un lado, se ha demostrado "gratings" adecuados para acoplo a guías de silicio convencionales. Por otra parte, se ha demostrado por primera vez el funcionamiento de "gratings" para guías de silicio tipo "slot" horizontal, que son un tipo de guía muy prometedora para aplicaciones de óptica no lineal. En relación con el acoplamiento a través de "inverted taper", se ha demostrado una estructura novedosa basada en este tipo de acoplamiento. Con esta estructura, importantes son los avances conseguidos en el empaquetado de fibras ópticas con el circuito de silicio. Su innovadora integración con estructuras de tipo "V-groove" se presenta como un medio para alinear pasivamente conjuntos de múltiples fibras a un mismo circuito integrado fotónico. También, se estudia el empaquetado de conjuntos de múltiples fibras usando acopladores tipo "grating", resultando en un prototipo de empaquetado de reducido tamaño.
Galán Conejos, JV. (2010). Addressing Fiber-to-Chip Coupling Issues in Silicon Photonics [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/9196
Palancia

La montée exponentielle du trafic de données liée au développement de l’interconnexion entre objets et personnes sur la toile nécessite de nouvelles technologies. Au cours de la dernière décennie, les peignes de fréquences optiques ont révolutionné le secteur des télécommunications, ouvrant la voie à une transmission de données à un débit de données auparavant inaccessible. Mis à part le domaine des télécommunications, les peignes de fréquences optiques ont été avantageusement exploités dans d’autres domaines comme la détection optique, la détection chimique, les horloges optiques… L'efficacité du phénomène de mélange à quatre ondes, qui sous-tend la génération des peignes de fréquences, dépend de manière significative des pertes par propagation dans les guides d’ondes optiques et, par conséquent, de la rugosité de ces derniers. De plus, l'absorption intrinsèque du matériau réduit l'efficacité des phénomènes non linéaires tout en contribuant à l’atténuation du signal lumineux dans le milieu optique de propagation. Grâce à la maturité des procédés de fabrication dits CMOS, la rugosité peut être réduite en optimisant la gravure, tandis que l’absorption peut être réduite par des traitements thermiques. L'utilisation d'un matériau CMOS permet donc une fabrication à faible coût et la co-intégration avec d’autres dispositifs optoélectroniques sur la même puce. Le nitrure de silicium sur isolant est une plateforme prometteuse pour la génération de peignes de fréquences optiques grâce à la faible absorption à deux photons dans ce matériau par rapport au silicium cristallin. Cependant, le nitrure présente une absorption dans la bande des télécommunications relié à la présence des liens moléculaires N-H. Tandis que des recuits à haute température ont été utilisés pour réduire le contenu en hydrogène du film et démontrer avec succès la génération de peignes de fréquence, ces procédés rendent la co-intégration monolithique de ces dispositifs en nitrure de silicium avec une optoélectronique à base de silicium très difficile, réduisant ainsi considérablement sa compatibilité avec les autres matériaux CMOS. Dans cette thèse, nous décrivons la conception, la fabrication et les caractérisations de circuits photoniques non-linéaires en nitrure de silicium sans recuit. En particulier, nous avons mis au point un procédé de fabrication de films de Si3N4 d'une épaisseur de 740 nm, sans utilisation de recuit et avec une maitrise de la gestion des contraintes typiquement associées à ce type de matériau pour l’optique non linéaire. Cette approche offre une compatibilité de fabrication technologique avec la photonique sur silicium. Des preuves expérimentales montrent que les micro-résonateurs utilisant de tels films de nitrure de silicium sans recuit sont capables de générer un peigne de fréquence s'étendant sur 1300-2100 nm via une oscillation paramétrique optique basée sur du mélange à quatre ondes. En allant encore plus loin, nous présentons également les travaux d’optimisation technologique portant sur des microrésonateurs en nitrure de silicium recuits avec des guides d’onde à fort confinement modal, qui nous ont permis d’atteindre des pertes de propagation record. Ces résultats ont été rendus possible grâce à une optimisation fine des étapes de gravure des guides d’onde ainsi qu’à l'utilisation de traitements thermiques-chimiques efficaces. Cette nouvelle approche nous a permis de démontrer par ailleurs des sources de peignes de fréquences intégrées sur puce utilisant des résonateurs en nitrure de silicium couplés par aboutement à un laser III-V DFB utilisé comme une pompe. Cette preuve de concept prouve la validité de notre plateforme de circuits photoniques non-linéaires en Si3N4 pour la réalisation de peignes de fréquences optiques ultra-compacts à faible consommation
The data traffic need for ultra-high definition videos as well as for the mobile data continues to grow. Within the last decade, optical frequency combs have revolutionized the telecommunications field and paved the way for groundbreaking data transmission demonstrations at previously unattainable data rates. Beside the telecommunications field, optical frequency combs brought benefits also for many other applications such as precision spectroscopy, chemical and bio sensing, optical clocks, and quantum optics. The efficiency of the four-wave mixing phenomenon from which the optical frequency comb arises critically depends on the propagation losses and consequently on the device roughness induced by the lithography and the etching processes. In addition, the bulk material absorption reduces the efficiency of the nonlinear phenomena. By using state-of-the-art complementary metal oxide semiconductor processes, the roughness can be reduced thanks to the maturity of the manufacturing, while the material bulk absorption can be reduced by thermal treatments. In addition, using a CMOS material enables a low-cost fabrication and the co-integration with electronic devices into the same chip. Silicon-nitride-on-insulator is an attractive CMOS-compatible platform for optical frequency comb generation in the telecommunication band because of the low two-photon absorption of silicon nitride when compared with crystalline silicon. However, the as deposited silicon nitride has a hydrogen related absorption in the telecommunication band. Although high-temperature annealing has been traditionally used to reduce the hydrogen content and successfully demonstrate silicon nitride-based frequency combs, this approach made the co-integration with silicon-based optoelectronics elusive, thus reducing dramatically its effective complementary metal oxide semiconductor compatibility. In this thesis, we report on the fabrication and test of annealing-free silicon nitride nonlinear photonic circuits. In particular, we have developed a process to fabricate low-loss, annealing-free and crack–free Si3N4 740-nm-thick films for Kerr-based nonlinear photonics, featuring a full process compatibility with front-end silicon photonics. Experimental evidence shows that micro-resonators using such annealing-free silicon nitride films are able to generate a frequency comb spanning 1300-2100 nm via optical parametrical oscillation based on four-wave mixing. In addition, we present the further optimized technological process related to annealed silicon nitride optical devices using high-confinement waveguides, allowing us to achieve record-low losses. This was enabled via a carefully tailored patterning etching process and an annealing treatment particularly efficient due to the already low hydrogen content in our as-deposited silicon nitride. Such improved Si3N4 platform allowed us to demonstrate on-chip integrated Kerr frequency comb sources using silicon nitride resonators that were butt-coupled to a III-V DFB laser used as a pump source. This proof of concept proves the validity of our approach for realizing fully packaged compact optical frequency combs

Manipulation of light at the nanoscale has the promise to enable numerous technological advances in biomedical sensing, optical communications, nano-mechanics and quantum optics. As photons have vanishingly small interaction cross sections, their interactions have to be mitigated by matters (i.e. quantum emitters, molecules, electrons etc.). Waveguides and cavities are the fundamental building blocks of the optical circuits, which control or confine light to specific matters of interest. The first half of the thesis (Chapters 2 & 3) focuses on how to design various photonic nanostructures to manipulate light on nano- to micro- scale, especially to modify the light-matter interaction properties. Chapter 2 discusses how nano-slot waveguides and photonic crystal nanobeam waveguides are able to modify the emission of quantum emitters, in a different way that normal ridge waveguides are not able to. Chapter 3 focuses on a more complicated and powerful structure: the photonic crystal nanobeam cavity. The design, fabrication and characterization of the photonic crystal nanobeam cavities are described and demonstrated in detail, which lays out the foundation of the biomedical sensing applications in the second half of the thesis. The second half of the thesis (Chapters 4 & 5) focuses on the application of photonic crystal nanobeam cavities in the label-free sensing of biomedical substances. Chapter 4 demonstrates detection of solutions with different refractive index (aceton, methanol, IPA etc.), glucose concentration, single polystyrene nanoparticles and single streptavidin bio-molecules. Chapter 4 proposes a novel nonlinear optical method to further enhance the sensitivity. Chapter 4 also demonstrates high quality nanobeam cavities fabricated in polymers, that open up a new route to decrease the cost, as well as to achieve novel applications with functional polymers. The broader impact of this technology lies in its potential of commercialization of a new generation of biosensors with high sensitivity and high integration. Chapter 5 discusses progresses towards instrumentation of the nanobeam cavity sensing technology for research & development apparatus, as well as point-of-care diagnostic tools.
Engineering and Applied Sciences

[ES] La optomecánica de cavidades se ocupa de la interacción entre la luz y la materia a través del efecto de presión de radiación cuando las ondas ópticas y mecánicas implicadas están confinadas en una cavidad. En estos sistemas optomecánicos, la interacción entre fotones y fonones da lugar a multitud de fenómenos en función de las condiciones en las que se excita el sistema. En particular, se pueden obtener dos regímenes distintos en los que se puede, o bien absorber fonones (denominado como enfriamiento de la cavidad), o bien éstos se pueden amplificar (régimen conocido como calentamiento de la cavidad). El primer régimen puede usarse, por ejemplo, para reducir la ocupación térmica del sistema y se usa comúnmente para aplicaciones relativas al procesado de información cuántica. Sin embargo, la amplificación de fonones, que puede ser desarrollada a temperatura ambiente, ha permitido conseguir alcanzar incluso las condiciones necesarias para obtener láseres de fonones, lo cual permite poder usar esta característica como elemento de referencia en aplicaciones relativas al procesado de señales de radiofrecuencia (RF). En esta tesis se aborda el confinamiento simultáneo y la interacción de fotones y fonones en estructuras periódicas y en guías no suspendidas desarrolladas en sistemas CMOS compatibles basados en tecnología de silicio. A través del estudio experimental de estas estructuras periódicas, hemos demostrado que las cavidades optomecánicas pueden actuar como elementos clave en el dominio de la fotónica de microondas, donde todo el procesado de la información puede ser realizado en el dominio óptico a través de la manipulación de fonones en este sistema. En particular, mostramos que un solo oscilador optomecánico puede actuar tanto como un oscilador local y un mezclador de RF, y éste puede operar como un conversor de frecuencias de señales de cadenas de datos reales. Para mejorar esta funcionalidad, también se demuestra que es posible obtener tanto peines de frecuencias ópticos así como múltiples modos mecánicos confinados, aumentando así su rendimiento. Por otro lado, con el objetivo de poder solventar las posibles limitaciones de estos sistemas, en esta tesis también se exploran diferentes configuraciones que permiten la interacción acusto-óptica simultánea en la misma estructura. Específicamente, se analiza la interacción optomecánica en discos de alto índice que soportan estados cuasi-ligados en el continuo así como una propuesta de guías no suspendidas que soportan altas ganancias de Brillouin. Este último estudio debería permitir el desarrollo de sistemas optomecánicos no suspendidos donde el problema de la pérdida de fonones hacia el sustrato se resuelva, hecho que permitiría enormemente simplificar la fabricación de estos sistemas optomecánicos en chips de silicio así como su uso en múltiples aplicaciones.
[CA] L'optomecànica de cavitats s'ocupa de la interacció entre la llum i la matèria a través de l'efecte de pressió de radiació quan les ones òptiques i mecàniques implicades estan confinades en una cavitat. En aquests sistemes optomecànics, la interacció entre fotons i fonons dona lloc a multitud de fenòmens en funció de les condicions de les condicions en les quals s'excita el sistema. En particular, es poden obtindre dos règims diferents en els quals es pot, o bé, absorbir fonons (denominat com a refredament de la cavitat), o bé, es poden amplificar (règim conegut com a calfament de la cavitat). El primer règim pot usar-se, per exemple, per a reduir l'ocupació tèrmica del sistema i s'usa comunament per a aplicacions relatives al processament d'informació quàntica. No obstant això, l'amplificació de fonons, que pot ser desenvolupada a temperatura ambient, ha permés aconseguir fins i tot les condicions necessàries per a obtindre làsers de fonons, la qual cosa permet poder usar aquesta característica com a element de referència en aplicacions relatives al processament de senyals de radiofreqüència (RF). En aquesta tesi s'aborda el confinament simultani i la interacció de fotons i fonons en estructures periòdiques i en guies no suspeses en sistemes CMOS compatibles basats en tecnologia de silici. A través de l'estudi experimental d'aquestes estructures periòdiques, hem demostrat que les cavitats optomecàniques poden actuar com a elements clau en el domini de la fotònica de microones, on tot el processament de la informació pot ser realitzat en el domini òptic a través de la manipulació de fonons en aquest sistema. En particular, vam mostrar que només un oscil·lador optomecànic pot actuar tant com un oscil·lador local i un mesclador de RF, i aquest pot operar com un convertidor de freqüències de senyals de cadenes de dades reals. Per a millorar aquesta funcionalitat, també es demostra que és possible obtindre tant tren de freqüències òptics així com múltiples modes mecànics confinats, augmentant així el seu rendiment. D'altra banda, amb l'objectiu de poder solucionar les possibles limitacions d'aquests sistemes, en aquesta tesi també s'exploren diferents configuracions que permeten la interacció acusto-òptica simultània en la mateixa estructura. Específicament, s'analitza la interacció optomecànica en discos d'alt índex que suporten estats quasi-lligats en el continu així com una proposta de guies no suspeses que suporten altes ganancies de Brillouin. Aquest últim estudi hauria de permetre el desenvolupament de sistemes optomecànics no suspesos on el problema de la pèrdua de fonons cap al substrat es resolga, fet que permetria enormement simplificar la fabricació d'aquests sistema optomecànics en xips de silici així com el seu ús en diverses aplicacions.
[EN] Cavity optomechanics deals with the interaction of light and matter through the radiation pressure effect, when the involved optical and mechanical waves are confined in a cavity. In optomechanical systems, photon and phonon interaction give rise to a plethora of phenomena as a function of the driving conditions of the system. Relative to that, two distinctive regimes can be obtained which enable either the absorption of phonons (cavity cooling) or their amplification (cavity heating). The first regime can be used to reduce the thermal occupancy of the system and it is commonly used for quantum processing information applications. However, the amplification of phonons, which can be performed at room temperature, has enabled to even reach phonon lasing conditions, a feature that could be used as a reference element for RF processing applications. In this thesis, we address the simultaneous confinement and interaction of photons and phonons in periodic structures and unreleased waveguides on CMOS-compatible silicon-based technology. Throughout the experimental study of those periodic structures, we demonstrate that optomechanical cavities can perform as key blocks in the microwave photonics domain where all the information processing can be performed in the optical domain through phonon manipulation. In particular, we show that a single optomechanical oscillator can perform as both a local oscillator and an RF mixer, and it can operate as a frequency-converted of real data stream signals. To improve its performance, it is also demonstrated that optical frequency combs can be obtained by means of this system and multiple mechanical mode confinement can also be achieved, thus improving the functionality of the system. On the other hand, in order to fulfill the possible limitations of those systems, we explore different configurations enabling the simultaneous acousto-optic interaction together into the same structure. Especially, optomechanical interaction in high-index disks supporting quasi-bound states in the continuum is addressed, as well as a proposal of unreleased waveguides supporting strong Brillouin gains is also reported. The last one should lead to unreleased optomechanical interacting systems where the issue of phonon leakage into the substrate is solved, which could enormously simplify the fabrication of optomechanical systems in silicon chips as well as their practical use in multiple applications.
This work has been carried out under the framework of the H2020 FET-Open EU project PHENOMEN. This Thesis was also supported by the Programa de Ayudas de Investigación y Desarrollo (PAID-01-16) de la Universitat Politècnica de València
Mercadé Morales, L. (2021). Phonons Manipulation in Silicon Chips Using Cavity Optomechanics [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/171461
TESIS

The goal of the research reported in this thesis is to establish the feasibility of a novel optical architecture for an optical route & select circuit switch suitable for implementation as a photonic integrated circuit. The proposed architecture combines Optical Phased Array (OPA) switch elements implemented as multimode interference coupler based Generalised Mach-Zehnder Interferometers (GMZI) with a planar Lüneburg lens-based optical transpose interconnection network implemented using graded metamaterial waveguide slabs. The proposed switch is transparent to signal format and, in principle, can have zero excess insertion loss and scale to large port counts. These switches will enable the low-energy consumption high capacity communications network infrastructure needed to provide environmentally-friendly broadband access to all. The thesis first explains the importance of switch structures in optical communications networks and the difficulties of scaling to a large number of switch ports. The thesis then introduces the Talbot effect, i.e. the self-imaging of periodic field distributions in free space. It elaborates on a new approach to finding the phase relations between pairs of Talbot image planes at carefully selected positions. The free space Talbot effect is mapped to the waveguide Talbot effect which is fundamental to the operation of multimode interference couplers (MMI). Knowledge of the phase relation between the MMI ports is necessary to achieve correct operation of the GMZI OPA switch elements. An outline of the design procedures is given that can be applied to optimise the performance of MMI couplers and, as a consequence, the GMZI OPA switch elements. The Lüneburg Optical Transpose Interconnection System (LOTIS) is introduced as a potential solution to the problem of excessive insertion loss and cross-talk caused by the large number of crossovers in a switch fabric. Finally, the thesis explains how a Lüneburg lens may be implemented in a graded ‘metamaterial’, i.e. a composite material consisting of ‘atoms’ arranged on a regular lattice suspended in a host by nano-structuring of silicon waveguide slabs using a single etch-step. Furthermore, the propagation of light in graded almost-periodic structures is discussed. Detailed consideration is given to the calibration of the local homogenised effective index; in terms of the local parameters of the metamaterial microstructure in the plane and the corrections necessary to accommodate slab waveguide confinement in the normal to the plane. The concept and designs were verified by FDTD simulation. A 4×4 LOTIS structure showed correct routing of light with a low insertion loss of -0.25 dB and crosstalk of -24.12 dB. An -0.45 dB excess loss for 2D analysis and an -0.83 dB insertion excess loss for 3D analysis of two side by side metamaterial Lüneburg lenses with diameter of 15 μm was measured, which suggests that the metamaterial implementation produces minimal additional impairments to the switch.

Silicon is the dominant material in Microelectronics. Building photonic devices out of silicon can leverage the mature processing technologies developed in silicon CMOS. Silicon is also a very good waveguide material. It is highly transparent at 1550nm, and it has very high refractive index of 3.46. High refractive index enables building high index contrast waveguides with dimensions close to the diffraction limit. This provides the opportunity to build highly integrated photonic integrated circuit that can perform multiple functions on the same silicon chip, an optical parallel of the electronic integrated circuit. However, silicon does not have some of the necessary properties to build active optical devices such as lasers and modulators. For Example, silicon is an indirect band gap material that can’t be used to make lasers. The centro-symmetric crystal structure in silicon presents no electro-optic effect. By contrast, electro-optic polymer can be engineered to show very strong electro-optic effect up to 300pm/V. In this research we have demonstrated highly compact and efficient devices that utilize the strong optical confinement ability in silicon and strong electro-optic effect in polymer. We have performed detailed investigations on the optical coupling to a slow light waveguide and developed solutions to improve the coupling efficiency to a slow light photonic crystal waveguides (PCW). These studies have lead to the demonstration of the most hybrid silicon modulator demonstrate to date and a compact chip scale true time delay module that can be implemented in future phased array antenna systems. In the future, people may be able to realize a photonic integrated circuit for optical communication or sensor systems using the devices we developed in our research.
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The continuous growth of electronic compute and memory nodes in terms of the number of I/O pins, bandwidth, and areal throughput poses major integration and packaging challenges associated with offloading multi-Tbit/s data rates within the few pJ/bit targets. While integrated photonics are already deployed in long and short distances such as inter and intra data centers communications, the promising characteristics of the silicon photonic platform set it as the future technology for optical interconnects in ultra short inter-chip distances. The high index contrast between the waveguide and the cladding together with strong thermo-optic and carrier effects in silicon allows developing a wide range of micro-scale and low power optical devices compatible with the CMOS fabrication processes. Furthermore, the availability of photonic foundries and new electrical and optical co-packaging techniques further pushes this platform for the next steps of commercial deployment. The work in this dissertation presents the current trends in high-performance memory and processor nodes and gives motivation for disaggregated and reconfigurable inter-chip network enabled with the silicon photonic layer. A dense WDM transceiver and broadband switch architectures are discussed to support a bi-directional network of ten hybrid-memory cubes (HMC) interconnected to ten processor nodes with an overall aggregated bandwidth of 9.6Tbit/s. Latency and energy consumption are key performance parameters in a processor to primary memory nodes connectivity. The transceiver design is based on energy-efficient micro-ring resonators, and the broadband switch is constructed with 2x2 Mach-Zehnder elements for nano-second reconfiguration. Each transceiver is based on hundreds of micro-rings to convert the native HMC electrical protocol to the optical domain and the switch is based on tens of hundreds of 2x2 elements to achieve non-blocking all-to-all connectivity. The next chapters focus on developing methods for controlling and monitoring such complex and highly integrated silicon photonic subsystems. The thermo-optic effect is characterized and we show experimentally that the phase of the optical carrier can be reliably controlled with pulse-width modulation (PWM) signal, ultimately relaxing the need for hundreds of digital to analog converters (DACs). We further show that doped waveguide heaters can be utilized as \textit{in-line} optical power monitors by measuring photo-conductance current, which is an alternative for the conventional tapping and integration of photo-diodes. The next part concerned with a common cascaded micro-ring resonator in a WDM transceiver design. We develop on an FPGA control algorithm that abstracts the physical layer and takes user-defined inputs to set the resonances to the desired wavelength in a unicast and multicast transmission modes. The associated sensitivities of these silicon ring resonators are presented and addressed with three closed-loop solutions. We first show a closed-loop operation based on tapping the error signal from the drop port of the micro-ring. The second solution presents a resonance wavelength locking with a single digital I/O for control and feedback signals. Lastly, we leverage the photo-conductance effect and demonstrate the locking procedure using only the doped heater for both control and feedback purposes. To achieve the inter-chip reconfigurability we discuss recent advances of high-port-count SiP broadband switches for reconfigurable inter-chip networks. To ensure optimal operation in terms of low insertion loss, low cross-talk and high signal integrity per routing path, hundreds of 2x2 Mach-Zehnder elements need to be biased precisely for the cross and bar states. We address this challenge with a tapless and a design agnostic calibration approach based on the photo-conductance effect. The automated algorithm returns a look-up table for all for each 2x2 element and the associated calibrated biases. Each routing scenario is then tested for insertion loss, crosstalk and bit-error rate of 25Gbit/s 4-level pulse amplitude modulation signals. The last part utilizes the Mach-Zehnder interferometers in WDM transceiver applications. We demonstrate a polarization insensitive four-channel WDM receiver with 40Gbit/s per channel and a transmitter design generating 8-level pulse amplitude modulation signals at 30Gbit/s.

The exponential growth of data generation–driven in part by the proliferation of applications such as high definition streaming, artificial intelligence, and the internet of things–presents an impending bottleneck for electrical interconnects to fulfill data center bandwidth demands. Links now require bandwidths in excess of multiple Tbps while operating on the order of picojoules per bit, in addition to constraints on areal bandwidth densities and pin I/O bandwidth densities. Optical communications built on a silicon photonic platform offers a potential solution to develop power efficient, high bandwidth, low attenuation, small footprint links, all while building off the mature CMOS ecosystem. The development of silicon photonic foundries supporting multi project wafer runs with associated process design kit components supports a path towards widespread commercial production by increasing production volume while reducing fabrication and development costs. While silicon photonics can always be improved in terms of performance and yield, one of the central challenges is the integration of the silicon photonic integrated circuits with the driving electronic integrated circuits and data generating compute nodes such as CPUs, FPGAs, and ASICs. The co-packaging of the photonics with the electronics is crucial for adoption of silicon photonics in datacenters, as improper integration negates all the potential benefits of silicon photonics. The work in this dissertation is centered around the development of silicon photonic multi chip module transceivers to aid in the deployment of silicon photonics within data centers. Section one focuses on silicon photonic integration and highlights multiple integrated transceiver prototypes. The central prototype features a photonic integrated circuit with bus waveguides with WDM microdisk modulators for the transmitter and WDM demuxes with drop ports to photodiodes for the receiver. The 2.5D integrated prototype utilizes a thinned silicon interposer and TIA electronic integrated circuits. The architecture, integration, characterization, performance, and scalability of the prototype are discussed. The development of this first prototype identified key design considerations necessary for designing multi chip module silicon photonic prototypes, which will be addressed in this section. Finally, other multi chip module silicon photonic prototypes will be overviewed. These include a 2.5D integrated transceiver with a different electronic integrated circuit TIA, a 3D integrated receiver, an active interposer network on chip, and a 2.5D integrated transceiver with custom electronic integrated circuits. Section two focuses on research that supports the development of silicon photonic transceivers. The thermal crosstalk from neighboring microdisk modulators as a function of modulator pitch is investigated. As modulators are placed at denser pitches to accommodate areal bandwidth density requirements in transceivers, this thermal crosstalk will become significant. In this section, designs and results from several iterations of custom microring modulators are reported. Custom microring modulators allow for scaling up the number of channels in microring transceivers by offering the ability to fabricate variable resonances and provide a platform for further innovation in bandwidth, free spectral range, and energy efficiency. The designs and results of higher order modulation format modulators, both microring based and Mach Zehnder based, are discussed. High order modulators offer a path towards scaling transceiver total throughput without having to increase the channel counts or component bandwidth. Together, the work in these two sections supports the development of silicon photonic transceivers to aid in the adoption of silicon photonics into data generating systems.

Large on-chip bandwidths required for high performance electronic chips will render optical components essential parts of future on-chip interconnects. Silicon photonics enables highly integrated photonic integrated circuit (PIC) using CMOS compatible process. In order to maximize the bandwidth density and design flexibility of PICs, vertical integration of electronic layers and photonics layers is strongly preferred. Comparing deposited silicon, single crystalline silicon offers low material absorption loss and high carrier mobility, which are ideal for multi-layer silicon PIC. Three different methods to build multi-layer silicon PICs based on single crystalline silicon are demonstrated in this dissertation, including double-bonded silicon-on-insulator (SOI) wafers, transfer printed silicon nanomembranes, and adhesively bonded silicon nanomembranes. 1-to-12 waveguide fanouts using multimode interference (MMI) couplers were designed, fabricated and characterized on both double-bonded SOI and transfer printed silicon nanomembrane, and the results show comparable performance to similar devices fabricated on SOI. However, both of these two methods have their limitations in optical interconnects applications. Large and defect-free silicon nanomembrane fabricated using adhesive bonding is identified as a promising solution to build multi-layer silicon PICs. A double-layer structure constituted of vertically integrated silicon nanomembranes was demonstrated. Subwavelength length based fiber-to-chip grating couplers were used to couple light into this new platform. Three basic building blocks of silicon photonics were designed, fabricated and characterized, including 1) inter-layer grating coupler based on subwavelength nanostructure, which has efficiency of 6.0 dB and 3 dB bandwidth of 41 nm, for light coupling between layers, 2) 1-to-32 H-tree optical distribution, which has excess loss of 2.2 dB, output uniformity of 0.72 dB and 3 dB bandwidth of 880 GHz, 3) waveguide crossing utilizing index-engineered MMI coupler, which has crossing loss of 0.019 dB, cross talk lower than -40 dB and wide transmission spectrum covering C-band and L-band. The demonstrated integration method and silicon photonic devices can be integrated into the CMOS back-end process for clock distribution and global signaling.
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Optical quantum networks are important for global use of quantum computers, and secure quantum communication. Those networks require storage devices for synchronizing or making queues of processing transferred quantum information. Practical quantum information networks should minimize loss of transmitted data (photons) and have high efficiency mapping when writing data on memories (solid state qubits). This requires strong light-matter interaction that is enabled by coupling qubits to optical cavities.

The first half of the thesis focuses on emerging candidates for promising qubits in silicon carbide (SiC). The optical and quantum properties of these color centers are discussed with focus on divacancies in 4H-SiC due to their long spin coherence time. Optically detected magnetic resonance of divacancies is shown, an essential technique for reading out the qubit state using the intensity of optical emission.

The second half of the thesis focuses on hybrid photonic devices for coupling to silicon carbide qubits. Hybrid devices are made of another layer of high refractive index material other than the qubit hosting material. Evanescent coupling to qubits close to the surface can be achieved without damaging the host material. Mainly the silicon (Si) on 4H-SiC hybrid ring resonator architecture is discussed starting from design, simulation to fabrication. The fabrication includes Si membrane transfer that is an important step to create a light confining layer on 4H-SiC. The final ring resonator device shows quality factors as high as 23000.

[ES] La revolución posibilitada por las aplicaciones fotónicas durante las últimas décadas ha dejado su impronta en la sociedad tal y como la conocemos actualmente. Ejemplos claros de este impacto están patentes en, por ejemplo, el enorme tráfico de datos generado por el uso de Internet o el empleo extendido de algunas técnicas biomédicas con fines diagnósticos o quirúrgicos, que no podrían entenderse sin el incesante desarrollo de los sistemas ópticos. La necesidad de combinar y miniaturizar estos sistemas para generar funcionalidades más avanzadas dio lugar al nacimiento de los circuitos fotónicos integrados (PICs), que es donde esta tesis comenzó a tomar forma. En este sentido, observamos limitaciones en términos de flexibilidad o reconfigurabilidad inherentes a la naturaleza guiada de la mayoría de los PICs realizados hasta el momento. En el caso de circuitos plasmónicos, observamos también limitaciones por las pérdidas que tienen las guías metálicas a altas frecuencias. La inclusión de estructuras inalámbricas (basadas principalmente en nanoantenas plasmónicas) en la capa fotónica surgió para mitigar estas pérdidas, abriendo también nuevas vías de investigación. Sin embargo, estos dispositivos aún presentaban rendimientos muy pobres como elementos puramente radiantes en el régimen de campo lejano. Para superar estas deficiencias, en este trabajo, introdujimos un enfoque novedoso en el desarrollo de dispositivos inalámbricos en la nanoescala, que dio forma a lo que llamamos on-chip wireless silicon photonics. Este nuevo concepto se apoyó en el uso de nanoantenas de silicio compatibles con procesos CMOS, que constituyen las estructuras clave que posibilitan un vasto catálogo de aplicaciones en redes fotónicas de comunicación o en sensores ultra-integrados, así como para la interconexión de sistemas dieléctricos-plasmónicos avanzados. En el ámbito de las comunicaciones, gracias a las sencillas reglas de diseño para adaptar la directividad de estas nanoantenas a diversas aplicaciones, pudimos demostrar por primera vez transmisiones inalámbricas de datos (mediante el uso de antenas altamente directivas) en redes on-chip reconfigurables o desarrollar dispositivos para generar a voluntad focos electromagnéticos de manera dinámica en espacios bidimensionales (gracias a antenas con una directividad más baja). Por otro lado, en el campo del biosensado, diseñamos y fabricamos un dispositivo lab-on-a-chip para la identificación de micropartículas, basado en el uso de antenas dieléctricas -presentando un rendimiento equiparable a los mejores diseños desarrollados hasta el momento- que incluye el subsistema óptico más compacto demostrado hasta la fecha. Finalmente, fuimos capaces de conectar experimentalmente y de manera eficiente antenas basadas en silicio con estructuras plasmónicas para el desarrollo de nuevas aplicaciones en la nanoescala, aunando las ventajas del on-chip wireles silicon photonics para comunicaciones en chip, conformación dinámica de haces o biosensado con las ventajas de la plasmónica para la manipulación e interacción con luz.
[CAT] La revolució habilitada per les aplicacions fotòniques durant les últimes dècades ha deixat la seua empremta en la societat actual tal com la coneixem. Exemples clars d'aquest impacte estan patents en, per exemple, l'enorme tràfic de dades generat per l'ús d'Internet o d'algunes tècniques biomèdiques amb fins diagnòstics o quirúrgics, que no es podrien entendre sense l'incessant desenvolupament dels sistemes òptics. La necessitat de combinar i miniaturitzar aquests sistemes per produir funcionalitats més avançades va donar lloc al naixement dels circuits fotònics integrats (PICs), que és on aquesta tesi va començar a prendre forma. En aquest sentit, observem limitacions en termes de flexibilitat o reconfigurabilitat inherents a la naturalesa guiada de la majoria dels PICs realitzats fins al moment. En el circuits plasmònics, tenim a mès les limitacions de les elevades pèrdues que les guies metàl·liques tenen a altes freqüències. La inclusió d'estructures sense fil (basades principalment en l'ús de nanoantenes plasmòniques) a la capa fotònica va sorgir per mitigar aquestes pèrdues, obrint també noves vies d'investigació. No obstant això, aquests dispositius encara presentaven rendiments molt pobres com a elements purament radiants en el règim de camp llunyà. Per superar aquestes deficiències, en aquest treball, vam introduir un enfocament innovador en el desenvolupament de dispositius sense fil a la nanoescala, que va donar forma al que anomenem on-chip wireless silicon photonics. Aquest nou concepte està basat en l'ús de nanoantenes de silici compatibles amb processos CMOS, que constitueixen les estructures clau que possibiliten un vast catàleg d'aplicacions en xarxes fotòniques de comunicació o en sensors ultra-integrats, així com per a la interconnexió de sistemes dieléctrics-plasmònics avançats. En l'àmbit de les comunicacions, gràcies a les senzilles regles de disseny per adaptar la directivitat de les antenes a les diverses aplicacions, vam poder demostrar per primera vegada transmissions de dades on-chip (mitjançant l'ús d'antenes altament directives) en xarxes reconfigurables o desenvolupar un dispositiu per generar a voluntat focus electromagnètics de manera dinàmica en espais bidimensionals (gràcies a antenes amb una directivitat més baixa). D'altra banda, en el camp del biosensing, vam dissenyar i fabricar un sensor lab-on-a-chip per a la classificació de micropartícules, basat en l'emprament d'antenes dielèctriques amb un rendiment a l'avantguarda dels millors dispositius de l'estat de l'art, que inclou el subsistema òptic més compacte demostrat fins al moment. Finalment, vam ser capaços de connectar experimentalment i de manera eficient antenes basades en silici amb estructures plasmònics per al desenvolupament de noves aplicacions en la nanoescala, unint els avantatges del on-chip wireless silicon photonics per a comunicacions en xip, conformació dinàmica de feixos o biosensat amb els avantatges de la plasmònica per a la manipulació e interacció amb llum.
[EN] The revolution sparked by photonic applications during the last decades has made its mark in society, as we currently know it. Clear examples of this impact are patent in, for instance, the colossal worldwide data traffic generated by the use of the Internet or the widespread utilization of some biomedical techniques for diagnostic or surgical purposes, which could not be understood without the ceaseless development of optical systems. The necessity of combining and miniaturizing these systems to enable advanced functionalities gave birth to the development of photonic integrated circuits (PICs), which is the main framework within which this thesis began to take shape. Along these lines, we noticed restricted limitations in terms of flexibility or reconfigurability inherent to the wired-based nature of most PIC implementations carried out so far. In the case of plasmonic circuitry, there are additional shortcomings arising from the prohibitive losses of metallic waveguides at very high frequencies. The inclusion of wireless structures (mostly based on plasmonic nanoantennas) at the photonic layer emerged to mitigate these limiting losses, also opening new research avenues. However, these devices still presented poor performances as purely radiating elements in the far-field regime. In order to overcome these lacks, in this work, we introduced a novel version to wireless approaches at the nanoscale in what we called on-chip wireless silicon photonics. This new concept was built upon the use of CMOS-compatible silicon-based nanoantennas, which constitute the key enabling structures of a diverse catalogue of applications in photonic communication networks or ultra-integrated sensors as well as for interfacing advanced dielectric-plasmonic systems. In the scope of communications, thanks to the easiness to tailor the antenna directivity, we were able to experimentally demonstrate on-chip data transmission flows in reconfigurable networks for the first time (by using highly directive antennas) or to develop dynamically tailor-made interference patterns to create focused spots at will on a 2D arrangement (enabled by antennas with a lower directivity). On the other hand, in the field of biosensing, we experimentally implemented a dielectric antenna-based lab-on-a-chip device for microparticle classification with state-of-the-art performance, which included the most compact optical subsystem demonstrated so far. Finally, we were able to efficiently interface silicon-based antennas to plasmonic systems to develop new advanced functionalities at the nanoscale, by putting together the advantages of on-chip wireless silicon photonics for on-chip communications, beam-shaping tailoring or lab-on-a-chip sensing with the advantages of plasmonics for light concentration and manipulation.
Lechago Buendía, S. (2019). All-dielectric nanoantennas enabling on-chip wireless silicon photonics [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/133074
TESIS

Today's supercomputers and cloud systems run many data-centric applications such as machine learning, graph algorithms, and cognitive processing, which have large data footprints and complex data access patterns. With computational capacity of large-scale systems projected to rise up to 50GFLOPS/W, the target energy-per-bit budget for data movement is expected to reach as low as 0.1pJ/bit, assuming 200bits/FLOP for data transfers. This tight energy budget impacts the design of both chip-scale networks and main memory systems. Conventional electrical links used in chip-scale networks (0.5-3pJ/bit) and DRAM systems used in main memory (>30pJ/bit) fail to provide sustained performance at low energy budgets. This thesis builds on the promising research on silicon-photonic technology to design system architectures and system management policies for chip-scale networks and main memory systems. The adoption of silicon-photonic links as chip-scale networks, however, is hampered by the high sensitivity of optical devices towards thermal and process variations. These device sensitivities result in high power overheads at high-speed communications. Moreover, applications differ in their resource utilization, resulting in application-specific thermal profiles and bandwidth needs. Similarly, optically-controlled memory systems designed using conventional electrical-based architectures require additional circuitry for electrical-to-optical and optical-to-electrical conversions within memory. These conversions increase the energy and latency per memory access. Due to these issues, chip-scale networks and memory systems designed using silicon-photonics technology leave much of their benefits underutilized. This thesis argues for the need to rearchitect memory systems and redesign network management policies such that they are aware of the application variability and the underlying device characteristics of silicon-photonic technology. We claim that such a cross-layer design enables a high-throughput and energy-efficient unified silicon-photonic link and main memory system. This thesis undertakes the cross-layer design with silicon-photonic technology in two fronts. First, we study the varying network bandwidth requirements across different applications and also within a given application. To address this variability, we develop bandwidth allocation policies that account for application needs and device sensitivities to ensure power-efficient operation of silicon-photonic links. Second, we design a novel architecture of an optically-controlled main memory system that is directly interfaced with silicon-photonic links using a novel read and write access protocol. Such a system ensures low-energy and high-throughput access from the processor to a high-density memory. To further address the diversity in application memory characteristics, we explore heterogeneous memory systems with multiple memory modules that provide varied power-performance benefits. We design a memory management policy for such systems that allocates pages at the granularity of memory objects within an application.