Monolithic integration of quantum dot lasers on 300 mm silicon photonic wafers

Rapid development of the Si photonics industry and its applications in data communication calls for the making of on-chip light sources integrated on the Silicon-on-Insulator (SOI) platform for mass production. Monolithic integration of III-V lasers, especially quantum dot (QD) lasers has gained increasing attention as a key technology to realize efficient, cost-effective, industrial-scale integration of light sources for Si photonics. In this thesis, we demonstrate for the first time, QD lasers grown and fabricated for electrically pumped lasing both on a planar template and in-pocket-template on 300 mm Si wafers. O-band edge-emitting in-pocket lasers are fabricated on Si with robust performance of continuous wave lasing up to 60 \textdegree C, a maximum double-sided output power of 124.8 mW at 20 °C and high fabrication yield. We also demonstrate for the first time, on-chip etched-facet lasers directly butt-coupled to SiN waveguides made on a 300-mm scale foundry-processed Si photonics wafer, characterized with fiber-coupling from on-chip edge couplers at waveguide output. Process developments addressing issues such as polycrystal deposition on surface, high aspect-ratio pocket geometry, and complications on growth interface affecting coupling are established. Perspectives on scaling this QD laser process on a 300 mm scale in a Si photonics foundry is also discussed, including remaining challenges of improving laser performance and yield, and prospects on the implementation of fully monolithic integration with a III-V/Si co-processing foundry

導波路結合を可能にする電流励起波長スケール金属クラッド半導体レーザの設計、作製と評価

学位の種別: 修士University of Tokyo(東京大学

A new conceptual design method to support rapid and effective mapping from product design specification to concept design

Conceptual design has a decisive impact on the product development time, cost and success. This paper presents a new conceptual design method for achieving rapid and effective mapping from product design specification (PDS) to concept design. This method can guide the creation of reasonable mapping among the PDS, behaviour parameters and structure parameters and to evaluate the rationality of performance parameters and structure parameters to confirm a reasonable conceptual design scheme. In this method, we establish a PDS-behaviour-structure conceptual design model to support the conceptual design of multi-disciplinary-oriented complex product system (CoPS) and develop a vector-based mapping tool in this method to support the rapid mapping, and demonstrate its feasibility and effectiveness by a case study. This method is not only supportive to realise the automation of a conceptual design process but also helpful to evaluate the conceptual design in the field of engineering design

Workpiece locating error prediction and compensation in fixtures

In machining process, fixture is used to keep the position and orientation of a workpiece with respect to machine tool frame. However, the workpiece always cannot be at its ideal position because of the setup error and geometric inaccuracy of the locators, clamping force, cutting force, and so on. It is necessary to predict and control the workpiece locating error which will result in machining error of parts. This paper presents a prediction model of a workpiece locating error caused by the setup error and geometric inaccuracy of locaters for the fixtures with one locating surface and two locating pins. Error parameters along 6 degrees of freedom can be calculated by the proposed model and then compensated by either using the “frame transformation” function of a numerical control (NC) system or modifying NC codes in post-processing. In addition, machining error caused by the workpiece locating error can be predicted based on a multi-body system and homogeneous transfer matrix. This is meaningful to fixture design and machining process planning. Finally, a cutting test has shown that the proposed method is practicable and effective

Integrated geometric error modeling, identification and compensation of CNC machine tools

This paper presents an integrated geometric error modeling, identification and compensation method for machine tools. Regarding a machine tool as a rigid multi-body system (MBS), a geometric error model has been established. It supports the identification of the 21 translational geometric error parameters associated with linear-motion axes based on a laser interferometer, and 6 angular geometric error parameters for each rotation axis based on a ball-bar. Based on this model, a new identification method is proposed to recognize these geometric errors. Finally, the identified geometric errors are compensated by correcting corresponding NC codes. In order to validate our method, a prototype software system has been developed, which can be used for conducting tests on any type of CNC machine tool with not more than five axes. An experiment has been conducted on a five-axis machine center with rotary table and tilting head; the results show that the integrated geometric error modeling, identification and compensation method is effective and applicable in multi-axis machine tools

Degradation Processes and Aging in Quantum Dot Lasers on Silicon

We discuss the physical processes responsible for the degradation of quantum-dot (QD) lasers epitaxially grown on silicon, based on combined electro-optical measurements and deep-level transient spectroscopy. The results shown that: a) during long-term operation, QD lasers show an increase in threshold current, correlated to a decrease in slope efficiency; b) the degradation is faster when the devices are stressed at high current levels, i.e. when the carriers occupy both the ground and the excited state; c) degradation can be explained by considering a recombination-enhanced defect reaction process, promoted by the escape of electrons from the quantum dots; d) the degradation rate is significantly dependent on the density of dislocations, as demonstrated by tests carried out on devices grown on native and silicon substrate; e) by modeling the degradation as due to defect diffusion, threshold voltage instability is ascribed to the recombination-enhanced diffusion of Be; f) through the use of a defect-trapping layer, degradation rate can be significantly reduced. The results provide relevant information for understanding the degradation physics of QD lasers for silicon photonics

Electrically pumped quantum-dot lasers grown on 300 mm patterned Si photonic wafers

Monolithic integration of quantum dot (QD) gain materials onto Si photonic platforms via direct epitaxial growth is a promising solution for on-chip light sources. Recent developments have demonstrated superior device reliability in blanket hetero-epitaxy of III-V devices on Si at elevated temperatures. Yet, thick, defect management epi designs prevent vertical light coupling from the gain region to the Si-on-Insulator waveguides. Here, we demonstrate the first electrically pumped QD lasers grown by molecular beam epitaxy on a 300 mm patterned (001) Si wafer with a butt-coupled configuration. Unique growth and fabrication challenges imposed by the template architecture have been resolved, contributing to continuous wave lasing to 60 °C and a maximum double-side output power of 126.6 mW at 20 °C with a double-side wall-plug efficiency of 8.6%. The potential for robust on-chip laser operation and efficient low-loss light coupling to Si photonic circuits makes this heteroepitaxial integration platform on Si promising for scalable and low-cost mass production

Search for Bc+→π+μ+μ−B_c^+\to\pi^+\mu^+\mu^- decays and measurement of the branching fraction ratio B(Bc+→ψ(2S)π+)/B(Bc+→J/ψπ+){\cal B}(B_c^+\to\psi(2S)\pi^+)/{\cal B}(B_c^+\to J/\psi \pi^+)

International audienceThe first search for nonresonant $B_c^+\to\pi^+\mu^+\mu^-$ decays is reported. The analysis uses proton-proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb$^{-1}$. No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio ${\cal B}(B_c^+\to\pi^+\mu^+\mu^-)/{\cal B}(B_c^+\to J/\psi \pi^+) < 2.1\times 10^{-4}$ at $90\%$ confidence level. Additionally, an updated measurement of the ratio of the $B_c^+\to\psi(2S)\pi^+$ and $B_c^+\to J/\psi \pi^+$ branching fractions is reported. The ratio ${\cal B}(B_c^+\to\psi(2S)\pi^+)/{\cal B}(B_c^+\to J/\psi \pi^+)$ is measured to be $0.254\pm 0.018 \pm 0.003 \pm 0.005$, where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the leptonic $J/\psi$ and $\psi(2S)$ decays. This measurement is the most precise to date and is consistent with previous LHCb results