This work experimentally and theoretically demonstrates the effect of excited state lasing on the reflection sensitivity of dual-state quantum dot lasers,showing that the laser exhibits higher sensitivity to external ...This work experimentally and theoretically demonstrates the effect of excited state lasing on the reflection sensitivity of dual-state quantum dot lasers,showing that the laser exhibits higher sensitivity to external optical feedback when reaching the excited state lasing threshold.This sensitivity can be degraded by increasing the excited-to-ground-state energy separation,which results in a high excited-to-ground-state threshold ratio.In addition,the occurrence of excited state lasing decreases the damping factor and increases the linewidth enhancement factor,which leads to a low critical feedback level.These findings illuminate a path to fabricate reflectioninsensitive quantum dot lasers for isolator-free photonic integrated circuits.展开更多
Atkamine is a complex marine pyrroloiminoquinone alkaloid that comprises a heptacyclic scaffold bearing five different heterocycles and four contiguous stereocenters,and therefore it is a highly challenging target for...Atkamine is a complex marine pyrroloiminoquinone alkaloid that comprises a heptacyclic scaffold bearing five different heterocycles and four contiguous stereocenters,and therefore it is a highly challenging target for synthetic chemists.We herein reported a modular synthetic strategy toward this alkaloid,featuring a formal [5+2] annulation and an asymmetric Michael addition.The efficient synthesis of the long-chain aliphatic aldehyde and chiral amino acetal fragments have been achieved.A simplified tetracyclic intermediate bearing the core structure of atkamine has been successfully constructed through the formal [5+2] annulation.展开更多
This work compares the four-wave mixing(FWM)effect in epitaxial quantum dot(QD)lasers grown on silicon with quantum well(QW)lasers.A comparison of theory and experiment results shows that the measured FWM coefficient ...This work compares the four-wave mixing(FWM)effect in epitaxial quantum dot(QD)lasers grown on silicon with quantum well(QW)lasers.A comparison of theory and experiment results shows that the measured FWM coefficient is in good agreement with theoretical predictions.The gain in signal power is higher for p-doped QD lasers than for undoped lasers,despite the same FWM coefficient.Owing to the near-zero linewidth enhancement factor,QD lasers exhibit FWM coefficients and conversion efficiency that are more than one order of magnitude higher than those of QW lasers.Thus,this leads to self-mode locking in QD lasers.These findings are useful for developing on-chip sources for photonic integrated circuits on silicon.展开更多
A unified protecting group-free approach to two stemarene and two betaerene diterpenoids through a bioinspired two-phase strategy has been developed,and three of them were obtained for the first time via chemical synt...A unified protecting group-free approach to two stemarene and two betaerene diterpenoids through a bioinspired two-phase strategy has been developed,and three of them were obtained for the first time via chemical synthesis.Starting from a common intermediate,two distinct tetracyclic frameworks containing diastereoisomeric bridged bicycles were constructed by a divergent ring reorganization strategy.Late-stage C–H functionalization through a xanthylation-oxygenation protocol furnished the corresponding oxygenated stereocenters or oxo functionality in high regio-and diastereoselective fashion within a complex hydrocarbon system.The stereochemical puzzles in(–)-2-acetoxybetaer13(17)-ene and(+)-7-acetoxybetaer-13(17)-ene were first predicted by the comparison of density functional theory(DFT)-nuclear magnetic resonance(NMR)data with the reported data and then unambiguously addressed through the total syntheses of natural products and three diastereomers.展开更多
基金National Key Research and Development Program of China(2022YFB2803600)National Natural Science Foundation of China(62204072,U22A2093)+1 种基金Basic and Applied Basic Research Foundation of Guangdong Province(2021A1515110076,2023A1515012304)Shenzhen Science and Technology Innovation Program(GXWD20220811163623002,RCBS20210609103824050)。
文摘This work experimentally and theoretically demonstrates the effect of excited state lasing on the reflection sensitivity of dual-state quantum dot lasers,showing that the laser exhibits higher sensitivity to external optical feedback when reaching the excited state lasing threshold.This sensitivity can be degraded by increasing the excited-to-ground-state energy separation,which results in a high excited-to-ground-state threshold ratio.In addition,the occurrence of excited state lasing decreases the damping factor and increases the linewidth enhancement factor,which leads to a low critical feedback level.These findings illuminate a path to fabricate reflectioninsensitive quantum dot lasers for isolator-free photonic integrated circuits.
基金the National Natural Science Foundation of China for financial support of this work by grants (Nos.21772164 and 21572187)the National Found for Fostering Talents of Basic Science (NFFTBS,No.J1310024)+1 种基金New Century Excellent Talents in University of Fujian Province (NECTFJ)Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT) for support。
文摘Atkamine is a complex marine pyrroloiminoquinone alkaloid that comprises a heptacyclic scaffold bearing five different heterocycles and four contiguous stereocenters,and therefore it is a highly challenging target for synthetic chemists.We herein reported a modular synthetic strategy toward this alkaloid,featuring a formal [5+2] annulation and an asymmetric Michael addition.The efficient synthesis of the long-chain aliphatic aldehyde and chiral amino acetal fragments have been achieved.A simplified tetracyclic intermediate bearing the core structure of atkamine has been successfully constructed through the formal [5+2] annulation.
基金Basic and Applied Basic Research Foundation of Guangdong Province(2021A1515110076)Center for Integrated Nanotechnologies,an Office of Science User Facility operated for the U.S.Department of Energy(DOE)Office of Science by Los Alamos National Laboratory(2021BC0057)DARPA PIPES(HR0011-19-C-0083).
文摘This work compares the four-wave mixing(FWM)effect in epitaxial quantum dot(QD)lasers grown on silicon with quantum well(QW)lasers.A comparison of theory and experiment results shows that the measured FWM coefficient is in good agreement with theoretical predictions.The gain in signal power is higher for p-doped QD lasers than for undoped lasers,despite the same FWM coefficient.Owing to the near-zero linewidth enhancement factor,QD lasers exhibit FWM coefficients and conversion efficiency that are more than one order of magnitude higher than those of QW lasers.Thus,this leads to self-mode locking in QD lasers.These findings are useful for developing on-chip sources for photonic integrated circuits on silicon.
基金Financial support from the National Natural Science Foundation of China(nos.22071205,21772164,and 21572187)NFFTBS(no.J1310024),and PCSIRT is acknowledged.
文摘A unified protecting group-free approach to two stemarene and two betaerene diterpenoids through a bioinspired two-phase strategy has been developed,and three of them were obtained for the first time via chemical synthesis.Starting from a common intermediate,two distinct tetracyclic frameworks containing diastereoisomeric bridged bicycles were constructed by a divergent ring reorganization strategy.Late-stage C–H functionalization through a xanthylation-oxygenation protocol furnished the corresponding oxygenated stereocenters or oxo functionality in high regio-and diastereoselective fashion within a complex hydrocarbon system.The stereochemical puzzles in(–)-2-acetoxybetaer13(17)-ene and(+)-7-acetoxybetaer-13(17)-ene were first predicted by the comparison of density functional theory(DFT)-nuclear magnetic resonance(NMR)data with the reported data and then unambiguously addressed through the total syntheses of natural products and three diastereomers.