High-speed Coherent Optical Communication with Isolator-free Heterogeneous Si/III-V Lasers

Coherent optical communication is considered as an indispensable solution to the ever-increasing demand for higher data rates. To reduce the cost and form factor of coherent transceivers, full integration of photonic devices including lasers, modulators, amplifiers, photodetectors, and other components is necessary. However, as fabricating optical isolators on chip remains extremely challenging, optical feedback, which can degrade the coherence of semiconductor lasers, becomes the main obstacle, thwarting large-scale photonic integration. An appealing solution to such a problem is to use semiconductor lasers with intrinsic insensitivity to optical feedback as the integrated light sources. The heterogenous Si/III-V lasers, with their built-in high-Q resonators, are expected to possess a robustness to optical feedback which exceeds by several orders of magnitude compared to commercial III-V distributed feedback (DFB) lasers, which will be validated here. We present data showing that the heterogeneous Si/III-V lasers can preserve their phase coherence under much larger optical feedback and therefore function without severe degradation in isolator-free coherent optical communication systems

YOLOv6: A Single-Stage Object Detection Framework for Industrial Applications

For years, the YOLO series has been the de facto industry-level standard for efficient object detection. The YOLO community has prospered overwhelmingly to enrich its use in a multitude of hardware platforms and abundant scenarios. In this technical report, we strive to push its limits to the next level, stepping forward with an unwavering mindset for industry application. Considering the diverse requirements for speed and accuracy in the real environment, we extensively examine the up-to-date object detection advancements either from industry or academia. Specifically, we heavily assimilate ideas from recent network design, training strategies, testing techniques, quantization, and optimization methods. On top of this, we integrate our thoughts and practice to build a suite of deployment-ready networks at various scales to accommodate diversified use cases. With the generous permission of YOLO authors, we name it YOLOv6. We also express our warm welcome to users and contributors for further enhancement. For a glimpse of performance, our YOLOv6-N hits 35.9% AP on the COCO dataset at a throughput of 1234 FPS on an NVIDIA Tesla T4 GPU. YOLOv6-S strikes 43.5% AP at 495 FPS, outperforming other mainstream detectors at the same scale~(YOLOv5-S, YOLOX-S, and PPYOLOE-S). Our quantized version of YOLOv6-S even brings a new state-of-the-art 43.3% AP at 869 FPS. Furthermore, YOLOv6-M/L also achieves better accuracy performance (i.e., 49.5%/52.3%) than other detectors with a similar inference speed. We carefully conducted experiments to validate the effectiveness of each component. Our code is made available at https://github.com/meituan/YOLOv6.Comment: technical repor

Highly enantioselective synthesis of lactam and sugar derivatives by chiral aminocatalysis and merging with transition metal catalysis

This thesis presented novel methodologies for enantioselectivesynthesis of highly functionalized lactam and sugar derivatives.Asymmetric organocatalysis, cooperative dual catalysis and one-pot multicomponent reaction strategies were applied for the construction of continuous and quaternary stereogenic center.In Chapter I, an unique strategy for enantioselective synthesis of bicyclic lactam N,S-acetals scaffolds was developed. The reaction intiates from an aminocatalyzed transformation. Next, the addition of thiol amine leads to the construction of bicyclic lactams via aimine/N,S-acetal formation/lactamization cascade sequence.Chapter II focuses on a stereodivergent synthesis of fluorinated lactams bearing two vicinal stereogenic centers by multicomponent reaction. The reaction proceeds via enantioselective Michael addition/imine formation/lactamization cascade process. The reaction solventused in the lactamizarion step gives switchable diastereoselectivity to the fluorinated quaternary stereocenter. DFT calculation revealed a mechanistic insight into the unexpected diastereoselectivity. The usefulness of fluorinated lactams was demonstrated in fluorinated drug analogue synthesis.Chapter III illustrates a new enantioselective allylic alkylation of acetonide protected trioses and furanosides by merging enamine catalysis with transition metal catalysis. An intrinsic sugar-assistedkinetic resolution mechanism between aldehyde and aminocatalystwas proposed and monitored in NMR studies.Chapter IV is about a new chiral amine-catalyzed C4’ α-aminomethylaction of furanoside and nucleoside derived C5’ aldehydes. The C4’ aminomethyl functionalized furanoside precursors have potentials fornew nucleoside analogue synthesis.Denna avhandling presenterar nya metoder för enantioselektiv syntes av högfunktionaliserade laktam- och sockerderivat. Asymmetrisk organokatalys, kooperativ dubbel katalys och flerkomponentreaktionsstrategier i en behållare användes för konstruktion av kontinuerliga och kvartära stereogena centra.I kapitel I utvecklades en unik strategi för enantioselektiv syntes av bicykliska laktam N,S-acetaler ställningar. Reaktionen initieras från en aminokatalyserad transformation. Därefter leder tillsatsen av tiolamin till konstruktionen av bicykliska laktamer via en imin/N,S-acetalbildning/laktamiseringskaskadsekvens. Kapitel II fokuserar på en stereodivergent syntes av fluorerade laktamer som bär två vicinala stereogena centra genom multi-komponentreaktion. Reaktionen fortskrider via enantioselektiv Michael-addition/iminbildning/laktamiseringskaskadprocess. Lösningsmedlet som används i laktamiseringssteget ger omkopplingsbar diastereoselektivitet till det fluorerade kvartära stereocentret. DFT-beräkningar gav en förklaring för den oväntade diastereoselektiviteten. Användbarheten av fluorerade laktamer demonstrerades med syntes av fluorerade läkemedelsanaloger. Kapitel III illustrerar en ny enantioselektiv allylisk alkylering av acetonidskyddade trioser och furanosider genom att kombinera enaminkatalys med övergångsmetallkatalys. En inneboende sockerassisterad kinetisk resolvering mellan aldehyd och aminokatalysator föreslogs och undersöktes i NMR-studier. Kapitel IV handlar om en ny kiral amin-katalyserad C4' α-aminometylering av furanosid och nukleosid härledda C5' aldehyder. De C4'-aminometylfunktionaliserade furanosidprekursorerna har potential för ny nukleosidanalogsyntes.Vid tidpunkten för framläggningen av avhandlingen var följande delarbete opublicerat: delarbete III och IV (inskickat).At the time of the defence the following paper was unpublished: paper III and IV (submitted).</p

Tuning the Sensitivity and Dynamic Range of Optical Oxygen Sensing Films by Blending Various Polymer Matrices

In this work, eight different types of optical oxygen sensing films were prepared by impregnating indicator and matrix solution on the surface of a polypropylene microporous filter membrane. The polymer matrix of the sensing films was ethyl cellulose (EC), polymethyl methacrylate (PMMA), and their blends with different mixing ratios. Scanning electron microscopy (SEM), laser confocal microscopy, and fluorescence spectrometer were used to investigate the morphologies and optical properties of the sensing films. Phase delay measurements under different oxygen partial pressures (PO2) and temperatures were applied to investigate the analytical performances of the sensing film for gaseous O2 monitoring. Results show that the response time of all the sensing films was extremely fast. The sensitivities and dynamic ranges of the sensing films with the blended polymer matrix were separately decreased and increased as the EC/PMMA ratio decreased, and the S-V curve of the sensing films blended with equal content of EC and PMMA exhibited good linearity under different temperatures, showing a promising prospect in practical application

Research on the Characteristics and Application of Two-Degree-of-Freedom Diagonal Beam Piezoelectric Vibration Energy Harvester

To overcome high periodic maintenance requirements, difficult replacement, and large application limitations of wireless sensor nodes powered by chemical batteries during the vibration control process of stiffened plates, a two-degree-of-freedom diagonal beam piezoelectric vibration energy harvester was proposed. Multidimensional energy harvesting and broadband work are integrated into one structure through the combined action of oblique angle, mass blocks, and piezoelectric beam. The mechanical model of the beam is established for theoretical analysis; the output characteristics of the structure are analyzed by finite element simulation; a piezoelectric energy harvesting experimental bench is built. The results show that: The structure has a wider harvesting band, multi-order resonant frequency, multi-dimensional energy harvesting, and higher output voltage and power than the traditional cantilever structures. The output performance of the specimens with 45° oblique angle, 5 g:5 g mass ratio, and 0.2 mm thickness of piezoelectric substrate is good in the frequency band of 10~40 Hz. When the excitation frequency is 28 Hz, the output voltage of the sextuple array structure reaches 19.20 V and the output power reaches 7.37 mW. The field experiments show that the harvester array can meet the requirements of providing auxiliary energy for wireless sensor nodes in the process of active vibration control of stiffened plates

Optical Single-Sideband WDM Nyquist 32-QAM SC-FDE Transmission system with Direct Detection

125 Gbit/s optical single side band (OSSB) Square-32QAM wavelength-divisionmultiplexed direct detection over 75.1km SSMF transmission has been successfully demonstrated with a subcarrier frequency band of 2.9 GHz and a channel frequency grid of 12.5GHz. ? OSA 2014.EI

Optical PAM-4 signal generation using a silicon Mach-Zehnder optical modulator

An analytic model is proposed to study the linearity performance of the silicon Mach-Zehnder optical modulator. According to the simulation results, we optimize the width of the silicon rib waveguide and the location of the PN junction to improve the linearity performance. The fabricated silicon Mach- Zehnder optical modulator has a spurious free dynamic range of 113.3 dB.Hz(2/3) and 88.9 dB.Hz(1/2) for the third-order intermodulation distortion and the second-order harmonic distortion. We also demonstrate the optical fourlevel pulse-amplitude-modulation (PAM-4) signal generation through the device. The generated optical PAM-4 signal is characterized at the rates up to 35 Gbaud. The BERs of the optical PAM-4 signals can reach 5.2x10(-6) at 20 Gbaud and 6.6x10(-5) at 32 Gbaud, which are much lower than the threshold of hard decision forward error correction (3.8x10(-3)). (C) 2017 Optical Society of AmericaProgram 863 [2015AA015503, 2015AA017001]; National Key R&amp;D Program of China [2017YFA0206402, 2016YFB0402501]; National Natural Science Foundation of China (NSFC) [61535002, 61505198, 61235001, 61575187, 61377067]SCI(E)ARTICLE1923003-230132

Highly diastereo and enantioselective synthesis of α-spiro-δ-lactams via organocascade reaction

An asymmetric synthesis of α-spiro-δ-lactam via organocascade reaction from easily accessible starting materials is reported. The catalytic sequence undergoes enantioselective Michael addition of β-ketoamide to α,β-unsaturated aldehyde catalysed by a secondary amine catalyst, followed by hemiaminal annulation. Optically enantiopure compounds with two contiguous stereogenic centres are obtained in good yields and excellent selectivities (up to &gt;20:1 dr and up to &gt;99% ee)