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In this study, zeta potentials of graphitic carbon nitride (g-C3N4) nanoparticles were detailedly investigated under various electrolytes, solution pH, and humic acid (HA) concentration conditions. The hydrodynamic radius of g-C3N4 nanoparticles was measured to be 388.9 ± 24 nm, and the specific surface area of the g-C3N4 nanoparticles was measured to be 46.2 m2 g−1. The absolute values of g-C3N4 zeta potentials significantly decreased with the increasing ionic strength (IS) due to the charge screening. Compared to the monovalent cation, the zeta potentials of g-C3N4 were less negative with the presence of divalent cations. In addition, K+ was more effective than Na+ in decreasing the absolute values of g-C3N4 zeta potentials, and Ca2+ was more effective than Mg2+ in decreasing the absolute values of g-C3N4 zeta potentials. When NaCl and CaCl2 were used as the electrolytes, the zeta potentials of g-C3N4 became less negative with the decreasing pH conditions. When FeCl3 and AlCl3 were used as the electrolytes, the zeta potentials of g-C3N4 became more positive with increasing solution pH due to the changing species of Fe3+ and Al3+. The zeta potentials of g-C3N4 were significantly more negative with the presence of HA. The results from this work indicated electrolytes, solution pH, and HA concentration conditions play a complex role in zeta potentials of g-C3N4 nanoparticles in aqueous environment.

Fibre lasers operating at the mid-IR have attracted enormous interest due to the plethora of applications in defence, security, medicine, and so on. However, no continuous-wave (CW) fibre lasers beyond 4 μm based on rare-earth-doped fibres have been demonstrated thus far. Here, we report efficient mid-IR laser emission from HBr-filled silica hollow-core fibres (HCFs) for the first time. By pumping with a self-developed thulium-doped fibre amplifier seeded by several diode lasers over the range of 1940–1983 nm, narrow linewidth mid-IR emission from 3810 to 4496 nm has been achieved with a maximum laser power of about 500 mW and a slope efficiency of approximately 18%. To the best of our knowledge, the wavelength of 4496 nm with strong absorption in silica-based fibres is the longest emission wavelength from a CW fibre laser, and the span of 686 nm is also the largest tuning range achieved to date for any CW fibre laser. By further reducing the HCF transmission loss, increasing the pump power, improving the coupling efficiency, and optimizing the fibre length together with the pressure, the laser efficiency and output power are expected to increase significantly. This work opens new opportunities for broadly tunable high-power mid-IR fibre lasers, especially beyond 4 μm.

Background The detection and management of intracranial aneurysms (IAs) are vital to prevent life-threatening complications like subarachnoid hemorrhage (SAH). Artificial Intelligence (AI) can analyze medical images, like CTA or MRA, spotting nuances possibly overlooked by humans. Early detection facilitates timely interventions and improved outcomes. Moreover, AI algorithms offer quantitative data on aneurysm attributes, aiding in long-term monitoring and assessing rupture risks. Methods We screened four databases (PubMed, Web of Science, IEEE and Scopus) for studies using artificial intelligence algorithms to identify IA. Based on algorithmic methodologies, we categorized them into classification, segmentation, detection and combined, and then their merits and shortcomings are compared. Subsequently, we elucidate potential challenges that contemporary algorithms might encounter within real-world clinical diagnostic contexts. Then we outline prospective research trajectories and underscore key concerns in this evolving field. Results Forty-seven studies of IA recognition based on AI were included based on search and screening criteria. The retrospective results represent that current studies can identify IA in different modal images and predict their risk of rupture and blockage. In clinical diagnosis, AI can effectively improve the diagnostic accuracy of IA and reduce missed detection and false positives. Conclusions The AI algorithm can detect unobtrusive IA more accurately in communicating arteries and cavernous sinus arteries to avoid further expansion. In addition, analyzing aneurysm rupture and blockage before and after surgery can help doctors plan treatment and reduce the uncertainties in the treatment process.

Anti-resonant hollow-core fibers have emerged as an important medium for high-power laser delivery due to their low optical nonlinearity and high damage threshold. However, current delivery systems of high-power laser based on anti-resonant hollow-core fibers mainly rely on free-space optical components, which limits long-term stability. Here, we report an all-fiber delivery of 2 kW laser with 85.4% transmission efficiency over 2.45 km, using a self-fabricated hollow-core fiber with a record low transmission loss of 0.168 dB/km at 1080 nm. Notably, we observed the phenomenon of stimulated Raman scattering amplified within the silica nested tubes for the first time. By effectively suppressing the Raman noise from the laser source, we achieve an all-fiber laser delivery without stimulated Raman scattering of silica glass. This work marks a significant breakthrough in multi-kilometer and multi-kilowatt power delivery that is potentially useful for industrial manufacturing, nuclear decommissioning, laser drilling in oil and so on. Recently, anti-resonant hollow-core fibers have emerged as an important medium for high-power laser delivery. Here, authors demonstrate a highly efficient, all-fiber delivery of 2 kW laser over 2.45 km, using a self-fabricated AR-HCF with a record low transmission loss of 0.168 dB/km at 1080 nm.

We demonstrate a 1.5 μm methane-filled hollow-core fiber (HCF) amplifier that delivers 7.1 W of narrow-linewidth (<0.1 nm), near-diffraction-limited (M2 < 1.2) pulsed Raman output. The system is pumped by a 1064 nm pulsed fiber laser and amplifies a 1543 nm continuous-wave seed via stimulated Raman scattering in methane. Using a 45-m HCF, we systematically investigated the influence of seed injection on key laser characteristics, covering the spectral profile, power scaling, and beam properties. This work provides an effective strategy for realizing high-performance fiber lasers in the 1.5 μm band.

Mid-infrared (MIR) fiber lasers are important for a wide range of applications in sensing, spectroscopy, imaging, defense, and security. Some progress has been made in the research of MIR fiber lasers based on soft glass fibers, however, the emission range of rare-earth ions and the robustness of the host materials are still a major challenge for MIR fiber lasers. The large number of gases provide a variety of optical transitions in the MIR band. When combined with recent advances in low-loss hollow-core fiber (HCF), there is a great opportunity for gas-filled fiber lasers to further extend the radiation to the MIR region. Here, a 4.8-μm CO-filled silica-based HCF laser is reported for the first time. This is enabled by an in-house manufactured broadband low-loss HCF with a measured loss of 1.81 dB/m at 4.8 μm. A maximum MIR output power of 46 mW and a tuning range of 180 nm (from 4644 to 4824 nm) are obtained by using an advanced 2.33-μm narrow-linewidth fiber laser. This demonstration represents the longest-wavelength silica-based fiber laser to date, while the absorption loss of bulk silica at 4824 nm is up to 13, 000 dB/m. Further wavelength expansion could be achieved by changing the pump absorption line and optimizing the laser structure.

In recent years, mid-infrared fiber lasers based on gas-filled photonic crystal hollow-core fibers (HCFs) have attracted enormous attention. They provide a potential method for the generation of high-power mid-infrared emissions, particularly beyond 4 μm. However, there are high requirements of the pump for wavelength stability, tunability, laser linewidth, etc., due to the narrow absorption linewidth of gases. Here, we present the use of a narrow-linewidth, high-power fiber laser with a highly stable and precisely tunable wavelength at 2 μm for gas absorption. It was a master oscillator power-amplifier (MOPA) structure, consisting of a narrow-linewidth fiber seed and two stages of Thulium-doped fiber amplifiers (TDFAs). The seed wavelength was very stable and was precisely tuned from 1971.4 to 1971.8 nm by temperature. Both stages of the amplifiers were forward-pumping, and a maximum output power of 24.8 W was obtained, with a slope efficiency of about 50.5%. The measured laser linewidth was much narrower than the gas absorption linewidth and the wavelength stability was validated by HBr gas absorption in HCFs. If the seed is replaced, this MOPA laser can provide a versatile pump source for mid-infrared fiber gas lasers.

Fiber lasers operating at 1.7 μm have significant application value in fields such as gas detection and material processing due to their characteristics, including compact structure and ease of thermal management. Based on the stimulated Raman scattering (SRS) of gas molecules in hollow-core fibers (HCFs), fiber gas Raman lasers (FGRLs) are a novel and effective method for generating 1.7 μm fiber lasers. We report here, to the best of our knowledge, the first FGRL based on the anti-resonant hollow-core fiber (AR-HCF) filled with sulfur hexafluoride (SF[sub.6]) molecules. A nanosecond pulsed fiber amplifier tunable from 1540 to 1560 nm was used to pump a 17.8-m-long AR-HCF filled with SF[sub.6] molecules. By virtue of the vibrational SRS of SF[sub.6] molecules, laser output in the range of 1748–1774 nm was achieved. At a gas pressure of 15 bar, a maximum average power output of ~3 W was obtained, corresponding to an optical-to-optical conversion efficiency of ~22%. The output linewidth of the Raman laser was measured to be approximately 2.1 GHz using a Fabry–Pérot (F-P) scanning interferometer. The research results enriched the methods for 1.7 μm fiber laser output.

A novel anti-resonant hollow-core fiber (AR-HCF) is proposed. The fiber uses cross-nested circular cladding tubes including single-nested and non-nested tubes in the near-infrared spectral region of 1.3–1.7 μm. All the anti-resonant tubes are used to minimize the confinement loss (CL) of the LP[sub.01] core mode. The non-nested tubes are also employed to achieve single-mode performance through strong mode coupling between the cladding mode and the LP[sub.11] core mode. The impact of the structural parameters on the CL of the modes is analyzed by using the finite element method (FEM). Optimization results indicate that the CLs of the LP[sub.01] mode and the LP[sub.11] mode are 0.18 dB/km and 5.88 × 10[sup.3] dB/km at 1.55 μm. Consequently, the higher-order mode extinction ratio (HOMER) achieves 3.27 × 10[sup.4]. Additionally, the mode field area of the fiber exceeds 4720 μm[sup.2] and the corresponding mode field diameter of the LP[sub.01] mode is more than 77 μm across the spectral region of 1.3–1.7 μm. In the practical applications, the fabrication tolerance is analyzed. The collapse of anti-resonant tubes within 0–2 μm and positional offsets between 0° and 4° both have minimal impact on fiber performance, thereby ensuring the stability of the system. Compared with other reported fibers, the proposed fiber demonstrates superior performance.

Fiber lasers operating at 2.8 μm have important applications in fields such as polymer material processing and medical surgery. Fiber gas lasers (FGLs) based on stimulated Raman scattering (SRS) in hollow-core fibers (HCFs) provide a superior approach to generating tunable, high-power laser at 2.8 μm. Here, we demonstrated a watt-level mid-infrared FGL with a tuning range from 2812 nm to 2862 nm by the SRS of methane molecules in a 26.7 m long HCF. By pumping with a tunable pulsed fiber amplifier at 1.5 μm, an average output power of approximately 1 W was obtained, with a low Raman threshold peak power of 1.7 kW. Additionally, we observed transverse mode instability (TMI) in the HCFs, which has rarely been reported previously, and propose that the TMI was caused by the thermal effect generated when methane molecules absorbed the pump laser. This work achieved both the wavelength flexibility and watt-level power of FGLs based on methane-filled HCFs in the 2.8 μm waveband. It also found that the TMI was a key factor limiting further improvement in output power. This work provides important experimental basis and optimization directions for the future realization of higher-power tunable fiber lasers in the 2.8 μm waveband.