Germanium photodetectors (Ge-PDs) are key components in silicon photonics (SiPh) to enable high-speed optical communications for various applications. Several works have been reported to improve the bandwidth, quantum efficiency, and manufacturing process of Ge-PDs. However, a significant trade-off between bandwidth and responsivity remains a major challenge in developing high-performance Ge-PDs for large-scale silicon photonic integrated circuits. Here, by co-optimizing the chemical mechanical polishing (CMP) process and device structure, ultra-thin Ge-PDs with high 3 dB bandwidth have been achieved. The dimensions of the Ge region and doping areas have also been optimized to attain a high-bandwidth, high-quantum-efficiency product. Consequently, we demonstrate lateral-PIN Ge-PDs with a high bandwidth of up to 100 GHz, 1.05 A/W responsivity at 1550 nm and <20nA dark current on 300 mm CMOS silicon-photonic process. Our work demonstrates that high-performance Ge-PDs with a simple fabrication process are feasible, which paves the way for developing next-generation 200 Gbaud intensity-modulated direct-detection (IMDD) and coherent optical systems.
Electronic dynamics at relativistic laser intensities have aroused extensive attention, and meanwhile, the enhancement of extreme-ultraviolet high-order harmonic generation (XUV-HHG) intensities has also been pursued. Here we propose, for the first time, a new scheme that involves the construction of a transient electrostatic field induced by electron nanobunches from relativistic intensity laser-irradiated double nanofoils, which then results in robust enhancement of XUV radiation in the transmitted direction, and experimentally demonstrate it. This scheme does not require purposely optimizing the laser contrast and pulse duration, and significant enhancement of harmonic radiation by more than one order of magnitude can be achieved as long as the laser is focused between the two foils. Our work offers novel insights into plasma-induced electronic dynamics at relativistic laser intensities and also proposes a robust scheme to realize significant enhancement of XUV-HHG at relativistic laser intensities, which promotes the application of XUV-HHG in atomic physics, ultrafast dynamics, and other fields.
Piezoelectric energy harvesting is essential for enabling self-powered wireless sensor networks in Internet of Things applications. This paper presents the first analysis of the voltage-blocking mechanism in synchronized switch harvesting on capacitors (SSHC) rectifiers, which occurs when the piezoelectric voltage magnitude exceeds a threshold determined by the transducer’s impedance characteristics. This phenomenon occurs under shock excitation or low-frequency conditions, yet has been previously overlooked in capacitor-based rectification techniques. To address this limitation, a dual-path SSHC (DSSHC) architecture is proposed, employing two parallel energy extraction paths at different voltage levels to extend the energy harvesting window. The high-voltage path handles normal operation, while the low-voltage path maintains energy transfer during voltage-blocking conditions. A decoupled dual-battery architecture eliminates charge redistribution losses between storage capacitors. Simulation results using an 8-stage implementation demonstrate 4.92% higher peak output power compared to conventional SSHC and elimination of voltage-blocking conditions.
2-Arylindoles are important motifs that serve as key components in a large variety of biologically active molecules and pharmaceuticals. Herein, we report a photoredox/Co-catalysis-enabled regioselective C2-arylation of indoles. This protocol allows for facile construction of a series of 2-arylindoles from structurally varied indoles and various aryl halides, featuring excellent regioselectivity, broad substrate scope, and good reaction efficiency. Mechanistically, the rational combination of photoredox-driven halogen-atom transfer (XAT) and Co-mediated desaturation ensured the success of this newly developed methodology.
In 2023, researchers from the University of Cambridge and the Paul Scherrer Institute (PSI) successfully demonstrated the feasibility of employing second-generation high-temperature superconducting (HTS) RE-Ba-Cu-O(REBCO) materials for undulator applications, achieving a magnetic field of 2.1 T with a 10 mm period and a 4 mm magnetic gap. This remarkable performance is primarily attributed to the high critical current density (Jc) of REBCO. However, REBCO also presents several challenges, including high production cost, complex fabrication procedures, and limited machinability. In contrast, although MgB₂ exhibits a lower Jc, it offers advantages such as ease of synthesis and machining, making it a promising candidate for undulator development. This study presents the design, preparation fabrication, and assembly of short-period MgB₂ bulk undulators, utilizing spark plasma sintered (SPS) MgB₂ bulks with a 16 mm period and a 4 mm magnetic gap, after 2D size optimization and 3D simulation, it is estimated that an undulator magnetic field of 1.75 T will be generated.
