Advanced Laser Technology (United Kingdom)

2D/3D perovskite-basedX-ray detectors have emerged asone of themost competitive candidates for future medical imaging owing to theirease of fabrication via solution processes and outstanding performance.Nevertheless, despite significant efforts in innovating materialsand device structures, it remains challenging to achieve high-quality2D/3D heterojunctions with a single and effective strategy. In thisstudy, we propose a gas-phase replacement reaction between propylamine(PA) and MAPbBr3 for the construction of the 2D (PA)2PbBr4–3D MAPbBr3 heterojunction.The growth of the (PA)2PbBr4 layer was influencedby the diffusion of PA. The quality of (PA)2PbBr4 could be controlled by finely choosing reaction conditions. X-raydetectors based on optimized 2D–3D perovskite heterojunctionsshowed a sensitivity of 25,143 μC Gyair–1 cm–2, lowest limit of detection of 1.33 μGyair s–1, dark current drift value of 2.27× 10–3 nA cm–1 s–1 V–1, and outstanding performance, which are allbetter than those of detectors based on MAPbBr3 singlecrystals. This research unveils the growth mechanism of 2D (PA)2PbBr4 perovskite via gas-phase replacement reactions,which are beneficial for the construction of high-quality 2D/3D perovskite-basedheterojunctions.

Vortex beams carrying orbital angular momentum have attracted increasing attention due to the helical wavefront, extensive high-dimensional state space, and cross-disciplinary applicability in fields such as high-capacity optical communication, optical manipulation, and super-resolution optical imaging. However, the intensity profile of vortex beams exhibits a topological charge-dependent annular structure, which imposes fundamental constraints on wavefront modulation flexibility, particularly in multi-mode coupling systems. In this study, we report a switchable perfect vortex beam (PVB) generator with high efficiency in the visible by combining spatially patterned photoalignment of nematic liquid crystal (LC) with multiplexed geometric phase profiles. Comprehensive simulations and experimental characterization demonstrate that the LC geometric-phase-based PVB generator produces high-quality vortex beams with spatially invariant intensity profiles across topological charges ranging from l = − 8 to + 8 and with an average conversion efficiency up to 86%. Moreover, we reveal that the PVB generator is switchable between left- and right-handed circularly polarized beams. This study demonstrates the feasibility of generating high-quality PVB through highly integrated flat LC photonic device, and may find applications in OAM multiplexing in quantum communication networks and ultrahigh-capacity photonic interconnects.

Continued loss reduction in hollow-core antiresonant fibers remains an essential challenge. This work presents an ultra-low loss hollow-core anti-resonant fiber design featuring a triple-nested cladding architecture with elliptical nested elements and six auxiliary compensation tubes located between the external circular tubes. Through fiber structure optimization using the finite element method, a broad transmission bandwidth from 1380-1700 nm and a confinement loss of less than 4.63×10-5 dB/km is achieved. At the 1550 nm operating wavelength, the structure exhibits a minimum confinement loss of 3.29×10-6 dB/km, which is two orders of magnitude lower than that of double-layer circular nested structures, and surface scattering loss of approximately 1.1×10-2 dB/km. At a 6 cm bending radius, the bending loss is below 5.8×10-3 dB/km. The low-loss performance of this fiber structure has potential applications including long-haul optical fiber communications, fiber gas lasers, and distributed sensing systems.

Output power of a laser device critically defines the application prospects. Colloidal quantum dots (QDs) have emerged as auspicious laser media; however, the exclusively low-power emission obscures the practical deployment. Here, we resolve this challenge by designing an architecture of QD laser with unprecedented peak powers in megawatt regime. The achievement is enabled by integrating the QDs with exceptional gain metrics with a seed-amplifier laser structure. Transient spectroscopy and theoretical simulation reveal that the narrow emission linewidth and large biexciton binding energy of the QDs act synergistically to enable an enhanced gain performance with submonoexcitonic threshold and record high–saturated gain cross section. A Littman-Metcalf cavity is designed to deliver the continuously tunable laser emission, and the synchronous amplification reaches the megawatt output. The high-power QD laser exhibits high spatial coherence, linear polarization, and operational endurance, which has proved effective as the pump source for spectroscopic research.

Fiber-integrated devices give THz applications advanced characteristics of connection with low insert loss, resistance on water vapor absorption, and flexible optical path adjustments. In this paper, an antiresonant fiber (ARF) structure with metasurfaced fiber core was proposed for polarization-dependent THz wave modulation, and the introduction of metasurface on the fiber core makes ARF have a high extinction with the modulation light and a low loss with the transmission light. Constructed by the metasurface coated low-density polyethylene (LDPE) film, the cladding tubes of the ARF were then sealed in a polytetrafluoroethylene (PTFE) shrinkable tube, forming the metasurfaced-core ARF. For the 1-THz wave, a 4-mm core-diameter ARF demonstrated a simulated loss of 0.18 dB for the transmission polarized light, whereas the absorption polarized loss exceeded 100 dB/m. A reasonable fabrication processing was proposed based on the method of "thin-film to optical fiber," and a metasurfaced-core ARF sample with a core diameter of 4mm and a length of 16cm was fabricated. Measured with THz time-domain spectroscopy (THz-TDS), the 16.cm length fiber sample showed a light transmission band at approximately the designed 1 THz and a strong polarization-dependent filtering capability with an approximately 7-dB difference in power spectral density.