Recently, a photonic alloy with non-trivial topological properties has been proposed, based on the random mixing of Yttrium Iron Garnet (YIG) and magnetized YIG rods. When the doping concentration of magnetized YIG rods is less than one, a chiral edge state (CES) of the topological photonic alloy appears in the frequency range of the non-trivial topological gap of the magnetized YIG crystal. In this work, we surprisingly find that by randomly mixing the Perfect Electric Conductor (PEC) and magnetized YIG rods in a square lattice, the photonic alloy system with appropriate doping concentrations can present CES in special frequency intervals even when both components support the propagation of bulk states. Analyzing the band structure of two components, we noticed a shift between the first trivial bandgap for PEC and the first topological bandgap for magnetized YIG. When calculating the transmission spectrum of the photonic alloy, we discovered that the frequency range for the topological gap gradually opens from the lower limit frequency of the bandgap for PEC to the bandgap for the magnetized YIG rods. The topological gap opening occurs as the doping concentration of magnetized YIG rods increases, creating an effective band alignment effect. Moreover, the topological gap for the photonic alloy is confirmed by calculating the reflection phase winding with the scattering method. Lastly, the gradual appearance of the CES is identified by applying Fourier transformation to real-space electromagnetic fields. Our work broadens the possibilities for flexible topological gap engineering in the photonic alloy system.
State Key Laboratory of Quantum Optics Technologies and Devices, Institute of Theoretical Physics, Shanxi University（山西大学量子光学技术与器件国家重点实验室理论物理研究所）；Sanli Honors College, Shanxi University（山西大学三立荣誉学院）；Institute of Laser Spectroscopy, Shanxi University（山西大学激光光谱研究所）；Collaborative Innovation Center of Extreme Optics, Shanxi University（山西大学极端光学协同创新中心）
Silicon Photonic Architecture for Training Deep Neural Networks with Direct Feedback Alignment
Queen’s University（女王大学）；University of British Columbia（不列颠哥伦比亚大学）；George Washington University（乔治华盛顿大学）；Princeton University（普林斯顿大学）；Vector Institute（向量研究所）
Sub-kHz-linewidth external-cavity laser (ECL) with Si$_{3}$N$_{4}$ resonator used as a tunable pump for a Kerr frequency comb
Karlsruhe Institute of Technology (KIT)（卡尔斯鲁厄理工学院）；LioniX International B.V.（LioniX国际有限公司）；École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）；Vanguard Automation GmbH（先锋自动化有限公司）；Deeplight S.A.（Deeplight股份有限公司）
将直接带隙III-V材料中的光学增益与先进光子集成电路提供的可调谐光学反馈相结合，是芯片级外腔激光器（ECL）的关键，可提供宽带可调谐性和低光学线宽。外部反馈电路可以使用低损耗氮化硅（Si $_{3}$ N $_{4}$）波导来有效地实现，其不遭受双光子吸收并且因此可以处理比常规硅光子高得多的功率电平。然而，将基于III-V族的增益元件与可调谐外部反馈电路共同集成在芯片级模块中仍然是一个挑战，需要技术要求苛刻的异构集成技术或昂贵的高精度多芯片组装。在这项工作中，我们展示了Si $_{3}$ N $_{4}$为基础的混合集成ECL，利用3D打印的结构，如腔内光子引线键合和小平面附加微透镜的低损耗光学耦合与宽松的对准公差，从而克服了需要主动对准，同时保持多芯片集成技术的充分灵活性。在一个概念验证实验中，我们展示了一个ECL提供了一个90 nm的调谐范围（1480 nm - 1570 nm），片上输出功率超过12 dBm和边模抑制比高达59 dB。我们实现了979 Hz的固有线宽，这是报告的可比反馈架构的最低值之一。III-V增益元件和基于Si $_{3}$ N $_{4}$的可调谐反馈电路之间的腔内光子引线键合的光学损耗总计约为（1.6 $\pm$ 0.2）dB。我们使用的ECL作为一个可调谐泵浦激光器产生一个耗散克尔孤子频率梳。据我们所知，我们的实验代表了第一次演示的单孤子克尔梳产生…
Alignment-free ultra-broadband parametric frequency conversion in lead-halide perovskites
Institute of Science and Technology Austria (ISTA)（奥地利科学技术研究所）；International Laser Centre（国际激光中心）；RCQI, Institute of Physics SAS（斯洛伐克科学院物理研究所量子凝聚态与量子信息研究中心）；King Abdullah University of Science and Technology（阿卜杜拉国王科技大学）；School of Materials Science and Engineering (MSE), Nanyang Technological University（南洋理工大学材料科学与工程学院）；Center for Renewable Energy and Storage Technologies (CREST), Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology（阿卜杜拉国王科技大学物理科学与工程学部可再生能源与储能技术研究中心）
