The American Institute for Manufacturing Integrated Photonics (AIM Photonics) is focused on developing an end- to- end integrated photonics ecosystem in the U.S., including domestic foundry access, integrated design tools, automated packaging, assembly and test, and workforce development. This paper describes how the institute has been structured to achieve these goals, with an emphasis on advancing the integrated photonics ecosystem. Additionally, it briefly highlights several of the technological development targets that have been identified to provide enabling advances in the manufacture and application of integrated photonics.

In recent years much effort has been carried out to make integrated photonics a widespread technology to be exploited in current optical communication industry. It is hoped by substituting microelectronics by photonic chips and keeping the light carried by optical fibers in light domain for further processing, the cost and speed of communications will be vastly improved. Although this transition is challenging in various aspects, here in this thesis some of these issues are discussed and addressed. In this thesis firstly the limitations of current simulation tools for analysis of wide range of photonic devices is pointed out. Structures based on photonic crystals are taken into consideration at this point which because of finely detailed structures have shown to be challenging to be analyzed by conventional tools. In this regard three different common structures based on photonic crystals in both resonant and non-resonant regimes have been considered: lamellar gratings, metamaterials for Lüneburg lens and Bragg gratings in a LC-DFB laser. For each structure, an analytical method or homogenization approach is proposed which is claimed to be faster for analysis of such components than numerical methods. Comparisons of the results with conventional numerical methods prove accuracies of each approach. Furthermore, fiber-to-chip coupling and polarization management are discussed as other important issues in the field of integrated photonics. Concerning polarization management, stepped waveguide approach will be introduced as the most promising approach for SOI and III-V substrates and designs based on this structure reported in literature are reproduced and inaccuracies are pointed out and corrected accordingly. Also regarding fiber-to-chip coupling, a critical appraisal of the most recent proposed structures for edge coupling will be offered and the results will be reproduced by simulation tools. At the end, based on detailed comparisons, the most encouraging approach with low insertion loss and easy fabrication steps is introduced and novel platform for easy butt coupling single mode fibers to the coupler structure is proposed.

In this thesis, ridge waveguide laser, quantum well intermixing, 1x1 and 2x2 optical switching and ring resonator with multimode-waveguide turning mirror couplers have been investigated. We develop a new design that the perturbation is the minimum when the crossing occurs at the self-image location in a low-loss multimode waveguide. We use a center-fold low-loss multimode waveguide with a single self image at the center. Such waveguides can cross at 90 degrees or 60 degrees at the center with minimal cross talk. One can reflect the incident mode into an intersecting waveguide by introducing an idea reflecting plane. In practice, the reflector is replaced by a plane for total internal reflection with correction for Goos-Hanchen shift. Passive component for£f = 1.41 £gm samples, 1x1 60-degree multimode-waveguide turning mirror, 1x1 90-degree multimode-waveguide turning mirror, 2x2 90-degree multimode-waveguide turning mirror and a single ring resonator with 2x2 multimode-waveguide turning mirror couplers have been fabricated. (1) The multimode-waveguide turning mirror coupler with cross coupling factor (K) of 0.15 is achieved by an etched facet with a correction for Goos-Hanchen shift. (2) The length of the multimode-waveguide turning mirror coupler is only 33% of the length of conventional straight 2x2 MMI coupler with K=0.15. (3) The circumference of the curve waveguide in this ring resonator is decreased by 50%. (4) The characterization of the InP-based single ring resonator incorporating 2x2 multimode-waveguide turning mirror couplers with K= 0.15 has a free spectral range of 82 GHz, a contrast of 4 dB, and a full-width at half-maximum (FWHM) of 0.24 nm for the drop port. (5) This single resonators in In0.53Ga0.47As/In0.53Ga0.26Al0.21As grown by molecular beam epitaxy (MBE), and In0.67Ga0.33As0.6P0.4/In0.71Ga0.29As0.74P0.26 grown by metal organic chemical vapor deposition (MOCVD) have been demonstrated, respectively. We have also developed quantum well intermixing technique for the photonic integration. (1) Argon plasma bombardment followed by rapid thermal annealing for InGaAs/InGaAlAs multiple-quantum-well structures grown by MBE has been found to strongly enhance the intensity of room-temperature photoluminescence signal by more than an order of magnitude. The strength of the photoluminescence signal is found to be dependent on the plasma RF power and bombardment time. The resulting blue shift of the photoluminescence wavelength due to quantum well intermixing is found to be under 15 nm. (2) Process combining inductively-coupled-plasma reactive ion etching (ICP-RIE) and SiO2 sputtering film has been investigated for the InGaAsP and InGaAlAs multi-quantum wells (MQWs). Optimal distance is of 300 nm for InGaAsP, and of 200-nm-thick for InGaAlAs between MQWs and the upper cladding by ICP-RIE and bombardment. The process resulted in a bandgap blue-shift of 90 nm for InGaAsP, and of 60 nm for InGaAlAs. The result is very useful to regrown, the sacrificing layer and to integrate the fabrication.

Photonic signal processing has been considered a promising solution to overcome the inherent bandwidth limitations of its electronic counterparts. Over the last few years, an impressive range of photonic integrated signal processors have been proposed with the technological advances of III-V and silicon photonics, but the signal processors offer limited tunability or reconfigurability, a feature highly needed for the implementation of programmable photonic signal processors. In this thesis, tunable and reconfigurable photonic signal processors are studied. Specifically, a photonic signal processor based on the III-V material system having a single ring resonator structure for temporal integration and Hilbert transformation with a tunable fractional order and tunable operation wavelength is proposed and experimentally demonstrated. The temporal integrator has an integration time of 6331 ps, which is an order of magnitude longer than that provided by the previously reported photonic integrators. The processor can also provide a continuously tunable fractional order and a tunable operation wavelength. To enable general-purpose signal processing, a reconfigurable photonic signal processor based on the III-V material system having a three-coupled ring resonator structure is proposed and experimentally demonstrated. The reconfigurability of the processor is achieved by forward or reverse biasing the semiconductor optical amplifiers (SOAs) in the ring resonators, to change the optical geometry of the processor which allows the processor to perform different photonic signal processing functions including temporal integration, temporal differentiation, and Hilbert transformation. The integration time of the signal processor is measured to be 10.9 ns, which is largely improved compared with the single ring resonator structure due to a higher Q-factor. In addition, 1st, 2nd, and 3rd of temporal integration operations are demonstrated, as well as a continuously tunable order for differentiation and Hilbert transformation. The tuning range of the operation wavelength is 0.22 nm for the processor to perform the three functions. Compared with the III-V material system, the CMOS compatible SOI material system is more cost effective, and it offers a smaller footprint due to the strong refractive index contrast between silicon and silica. Active components such as phase modulators (PMs) can also be implemented. In this thesis, two photonic temporal differentiators having an interferometer structure to achieve active and passive fractional order tuning are proposed and experimentally demonstrated. For both the active and passive temporal differentiators, the fractional order can be tuned from 0 to 1. For the active temporal differentiator, the tuning range of the operation wavelength is 0.74 nm. The use of the actively tunable temporal differentiator to perform high speed coding with a data rate of 16 Gbps is also experimentally demonstrated.

Thesis advisor: Michael J. Naughton / For many centuries, physicists and engineers have explored the creation, manipulation and detection of light. Only within the past century, however, have fabrication techniques advanced to the point where individual photons can be generated, manipulated, and measured. These advances have brought us to the point we are at today, where photonic devices are set to revolutionize the fields of computing, sensing and quantum information, to name a few. Despite the promise of these devices, scientists are still working to fully understand the light-matter interactions that govern their behavior. In this thesis, we uniquely characterize the behavior of certain photonic devices in an effort to understand the underlying physical principles that define them. Of particular interest to us is imaging via near-field scanning optical microscopy (NSOM) of photonic integrated circuit (PIC) elements with high quality factors (Q), such as microring resonators and photonic crystal cavities (PhCs). While these elements are becoming ubiquitous in emerging PIC designs, they have remained difficult to accurately image due to their high sensitivity to small perturbations (i.e. the NSOM probe). We solve this problem by controllably modulating the NSOM tip-sample distance and reducing the size of the probe. Finite element model computer simulations demonstrate that both of these adjustments decrease the tip sample interaction. We then apply this knowledge to generate first of their kind 50 nm resolution NSOM images of high Q resonant PIC devices. Importantly, aside from being accurate, the proposed NSOM technique is also facile and non-destructive. In addition to local field exploration of PIC elements, we explore non-classical optical transmission through sub-wavelength apertures in metallic films. We demonstrate that these interesting features arise from photonic wave interference. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

<p>The integration of planar on-chip light sources is a bottleneck in the implementation of portable planar chip-scale photonic integrated sensing systems, integrated optical interconnects, and optical signal processing systems on platforms such as Silicon (Si) and Si-CMOS integrated circuits. A III/V on-chip laser source integrated onto Si needs to use standard semiconductor fabrication techniques, operate at low power, and enable efficient coupling to other devices on the Si platform.</p><p>In this thesis, thin film strain compensated InGaAs/GaAs single quantum well (SQW) separate confinement heterostructure (SCH) edge emitting lasers (EELs) have been implemented with patterning on both sides of the thin film laser under either growth or host substrate support, with the devices metal/metal bonded to Si and SiO₂/Si substrates. Gain and index guided lasers in various configurations fabricated using standard semiconductor manufacturing processes were simulated, fabricated, and experimentally characterized. Low threshold current densities in the range of 250 A/cm<super>2</super> were achieved. These are the lowest threshold current densities achieved for thin film single quantum well (SQW) lasers integrated on Si reported to date, and also the lowest reported, for thin film lasers operating in the 980 nm wavelength window.</p><p>These thin film EELs were also integrated with photolithographically patterned polymer (SU-8) waveguides on the same SiO₂/Si substrate. Coupling of the laser and waveguide was compared for the cases where an air gap existed between the thin film laser and the waveguide, and in which one facet of the thin film laser was embedded in the waveguide. The laser to waveguide coupling was improved by embedding the laser facet into the waveguide, and eliminating the air gap between the laser and the waveguide. Although the Fresnel reflectivity of the embedded facet was reduced by embedding the facet in the polymer waveguide, leading to a 27.2% increase in threshold current density for 800 &mum long lasers, the slope efficiency of the L-I curves was higher due to preferential power output from the front (now lower reflectivity) facet. In spite of this reduced mirror reflectivity, threshold current densities of 260 A/cm<super>2</super> were achieved for 1000 &mum long lasers. This passively aligned structure eliminates the need for precise placement and tight tolerances typically found in end-fire coupling configurations on separate substrates.</p> / Dissertation

Bends and splitters are typically the fundamental limiting waveguide components in reducing the size of planar lightwave circuits (PLCs) based on waveguides that have a low core/clad refractive index contrast, such as silicon-on-insulator (SOI) rib waveguides. This dissertation presents a solution to this problem in the form of trench-based bends (TBBs) and trench-based splitters (TBSs). Emphasis is placed on experimental demonstration of these components and their integration into practical devices exhibiting significant size reduction. First, a compact and low loss silicon-on-insulator rib waveguide 90◦ TBB is demonstrated based on an etched vertical interface and total internal reflection (TIR) realized by a trench filled with SU8. The measured loss for TE polarization is 0.32 dB ± 0.02 dB/bend at a wavelength of 1.55 μm, which is the best reported in literature. Next, 90◦ TBSs are reported in which each splitter occupies an area of only 11 μm x 11 μm. These components require fabrication of trenches with a nearly 10:1 aspect ratio. A variety of single TBSs are fabricated having different trench widths. The relative amount of power directed into the transmission and reflection arms of the splitters is measured. The TBS reflection and transmission ratio agrees with three dimensional (3D) finite difference time domain (FDTD) predictions. An 82 nm wide trench filled with index matching fluid is experimentally shown to have a reflection/transmission splitting ratio of 49/51 at a wavelength of 1550 nm. To increase the fabrication yield of TBSs, the splitter angle is modified from 90◦ to 105◦, which permits the trench width to be increased to 116 nm for a 50/50 splitter using SU8 as the trench fill material. The fabrication and measurement of compact 105◦ TBBs and TBSs are reported followed by their integration into 1 x 4, 1 x 8, and 1 x 32 trench-based splitter networks (TBSNs). The measured total optical loss of the 1 x 32 TBSN is 9.15 dB. Its size is only 700 μm x 1600 μm for an output waveguide spacing of 50 μm. Finally, a compact SOI trench-based ring resonator (TBRR) composed of 90◦ TBBs, TBSs, and rib waveguides is demonstrated. A TBRR with a ring circumference of 50 μm occupies an area of 20 x 20 μm. The free spectral range (FSR) is as large as 14 nm. By changing the trench fill material from SU8 (n = 1.57) to index fluid (n = 1.733), the peak wavelength can be shifted ∼2 nm. Fabricated TBSNs and TBRRs demonstrate that large size reductions are possible for devices based on TBBs and TBSs. The net result is bend and splitter configurations with a size that is essentially independent of core/clad refractive index contrast. The approach developed in this dissertation is applicable to a wide range of waveguide material systems that have small core/clad refractive index contrast.

Silicon photonics is one of the most exciting and fastest growing photonic technologies in recent years. The salient feature of this technology is its compatibility with the mature silicon IC manufacturing based on complementary metal-oxide semiconductor (CMOS) processes widely used in microelectronic industry. Another motivation is the availability of high-quality silicon-on-insulator (SOI) planar waveguide circuits that offer strong optical confinement due to the high index contrast between silicon (n=3.45) and SiO2 (n=1.45). This opens up miniaturization and very large scale integration of photonic devices allowing photonic integrated circuits for a wide range of applications and markets, from optical telecommunications to bio-photonic devices or precise fibre sensors. Optical modulators are key building-blocks for high speed signal transmission and information processing in any photonic interconnection solution. The work developed in this thesis, as part of the objectives of the European project HELIOS in which it is framed, is essentially focused on realizing compact and efficient modulators integrated on silicon chips. The thesis consists of three main chapters as well as the concluding section on the work accomplished. Chapter one is aimed at giving a general description of the benefits of using silicon photonics, showing its challenges and opportunities as well as at giving a deeply overview of all issues related to the electro-optic modulation. Chapter two is devoted to develop silicon modulators with high features for digital applications. Specifically, new optical structures different to the conventional ones are presented with the aim of enhancing the modulation performance or at least several critical parameters in the modulation. Chapter three is dedicated to the analog applications. The concept of microwave photonics is described as well as different researches carried out in the analog scope for application in the field of integrated microwave photonics, all of them using CMOS-compatible electro-optic silicon modulators which validate the potential of silicon photonics as a promising approach for enabling the development of integrated microwave photonics applications. Finally, conclusions on the work realized are provided in Chapter 4. / La fotónica de silicio es una de las tecnologías fotónicas que está experimentando un crecimiento más excitante y rápido en los últimos años. La característica más destacada de esta tecnología es su compatibilidad con las maduras técnicas de fabricación de circuitos integrados de silicio basadas en los procesos ¿complementary metal-oxide semiconductor¿ (CMOS) ampliamente utilizados en la industria microelectrónica. Otra motivación es la disponibilidad de circuitos de guía de ondas planas de silicio sobre aislante (SOI) de alta calidad que ofrecen un fuerte confinamiento óptico debido al alto contraste índices entre el silicio (n=3,45) y el SiO2 (n = 1,45). Esto abre las puertas a la miniaturización y a la integración a gran escala de dispositivos fotónicos lo que resulta en circuitos fotónicos integrados para una amplia gama de aplicaciones y mercados, desde telecomunicaciones ópticas a dispositivos bio-fotónicos o sensores de fibra precisos. Los moduladores ópticos son elementos básicos fundamentales para la transmisión de señales a alta velocidad y el procesado de información en cualquier solución de interconexión fotónica. El trabajo desarrollado en esta tesis, como parte del los objetivos del proyecto Europeo HELIOS en el que está enmarcada, se centra fundamentalmente en realizar moduladores compactos y eficientes, integrados en chips de silicio. La tesis consiste en 3 capítulos principales así como una sección de conclusiones del trabajo conseguido. El capítulo uno está destinado a dar una descripción general de los beneficios del uso de la fotónica de silicio, mostrando sus retos y oportunidades, así como a dar una visión profunda de todos los aspectos relacionados con la modulación electro-óptica. El capítulo dos está dedicado a desarrollar moduladores de silicio de altas prestaciones para aplicaciones digitales. Específicamente, se presentan nuevas estructuras ópticas diferentes a las convencionales con el objetivo de mejorar el rendimiento de la modulación o al menos algunos parámetros críticos en la modulación. El tercer capítulo se dedica a las aplicaciones analógicas. Se describe el concepto de la fotónica de microondas, así como diferentes investigaciones llevadas a cabo en el ámbito analógico para su aplicación en el campo de la fotónica integrada de microondas, todas ellas usando moduladores electro-ópticos de silicio compatibles con los procesos de fabricación CMOS, lo que valida el potencial de la fotónica de silicio como un prometedor enfoque para permitir el desarrollo de aplicaciones de la fotónica integrada de microondas. Por último, las conclusiones sobre el trabajo realizado se proporcionan en el Capítulo 4. / Gutiérrez Campo, AM. (2013). Development of integrated silicon photonics modulation devices for digital and analog applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/33330

El proyecto consistirá en implementar funcionalidades fotónicas avanzadas sobre silicio tales como conmutación ultra rápida o la realización de puertas lógicas todo ópticas. Para ello se emplearán efectos no lineales del silicio basados en el efecto Kerr, producido por el coeficiente no lineal de tercer orden chi(3) .Los dispositivos deberán funcionar al menos a 40Gbps para que sean competitivos con los dispositivos actuales de última generación. También deberán ser compatibles con tecnología CMOS, lo cual es crucial para que la fabricación se pueda realizar a gran escala a precios competitivos. / Matres Abril, J. (2014). Ultrafast, CMOS compatible, integrated all optical switching [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/37984

Semiconductor lasers are considered essential for the advancement in the field of photonics where compact and energy-efficient lasers are necessary. Advancements in integrated photonic technologies will help push the performance of semiconductor lasers in the coming years and expand the technology to several other applications. Semiconductor lasers offer several key features such as high energy efficiency, mass production, availability at a myriad of wavelengths, and high integration capabilities. However, limitations in noise performance, pulse energy, and duration hold back semiconductor lasers from being utilized to their full potential. This dissertation reviews the utilization and development of external techniques that enable semiconductor mode-locked lasers to be used in multi-photon imaging and microwave photonic applications. We first review a two-color external cavity mode-locked laser system operating at wavelengths 834 nm and 974 nm that can generate synchronized picosecond pulses with peak powers exceeding 80 W and 100 W respectively. We verify the feasibility of this system to induce non-linear processes by demonstrating two-photon excitation in commercially available dyes. Next, we introduce the concepts of optical injection locking and discuss the development of a multi-tone optical self-injection locking technique to improve the noise performance and optical linewidth of a chip-scale InP based mode-locked laser. We utilize a Fabry-Perot etalon as the optical comb filter, which also serves to suppress the super-mode noise that arises from external cavity feedback. In addition to this, we also implement a coupled opto-electronic loop and reference it to an external RF source demonstrating exceptional timing stability. This approach along with the usage of fully integrated and ultra-compact components in subsequent versions has the potential to realize compact frequency comb lasers for microwave photonic and other practical applications.