Herein, hybrid nanoparticles composed of a red-emitting conjugated oligomer (COL) and gold nanoparticles (Au-NPs) were prepared through a one-pot synthetic method in which the oligomer acts as a reducing agent as well as a matrix to wrap the newly formed Au nanoparticles. These hybrid nanoparticles (COL-Au-NPs) exhibited photodynamic and photothermal activity against both Gram-positive and Gram-negative bacterial strains. They were also proven to possess high photostability and thermal reversibility. Dark cytotoxicity of COL-Au-NPs toward pathogens and mammalian breast cancer cells (MCF-7) reduced significantly upon complexation with cucurbit[7]­uril while preserving their light-induced cytotoxic activity when irradiated with a 915 nm laser for photothermal therapy and white light for photodynamic therapy, respectively. Furthermore, these nanoparticles have cellular imaging capability because of their intrinsic fluorescence characteristics and can be used in image-guided therapy.

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We demonstrate a 1018 nm ytterbium-doped all-fiber laser pumped by tunable pump sources operating in the broad absorption spectrum around 915 nm. In the experiment, two different pump diodes were tested to pump over a wide spectrum ranging from 904 to 924 nm by altering the cooling temperature of the pump diodes. Across this so-called pump wavelength regime having a 20 nm wavelength span, the amplified stimulated emission (ASE) suppression of the resulting laser was generally around 35 dB, showing good suppression ratio. Comparisons to the conventional 976 nm-pumped 1018 nm ytterbium-doped fiber laser were also addressed in this study. Finally, we have tested this system for high power experimentation and obtained 67% maximum optical-to-optical efficiency at an approximately 110 W output power level. To the best of our knowledge, this is the first 1018 nm ytterbium-doped all-fiber laser pumped by tunable pump sources around 915 nm reported in detail.

Cladding light strippers (CLSs) are vital and one of the critical components for high-power fiber laser applications. In this study, we show the first studies of the formation mechanisms and optimum conditions of a CLS device using a buffered oxide etchant by a combined method of stain (wet) etching and vapor-phase etching. This highpower CLS was shown to result in a stripping performance of ∼17.2 dB at the launched power of 333 W (pump limited). The thermal imaging demonstrates that the maximum temperature reached when operating the device at maximum launched power was ∼75°C. The atomic force microscopy (AFM) results show that the combined method yields crystal-like structures with the height in microscales, whereas other conventional methods give only nanoscale roughness. The method also preserves the diameter of the CLS device close to the bare fiber with about 10 μm tapering leads to a high surface area to strip unwanted light, which is good for heat dissipation. The combined method possesses the outcome of two methods, including both the crystal-like structures and nanosized hillocks, resulting in high-power stripping performance and robustness.

Ytterbium (Yb)-doped optical fibers are mainly used in the fiber laser resonator and amplifier systems. These systems have been widely utilized for applications in air and space, the defense industry, and the medical field. Particularly for the applications yielding operation in harsh environments consisting of radiation, it is essential to determine the radiation hardness of the Yb-doped optical fibers and their long-term performance in such environments. This study analyzed the optical properties of four different Yb-doped aluminophosphosilicate fibers before and after gamma irradiation. For each fiber, the effect of different total dose values including 0.5, 1, 10, and 50 kGy were determined at different operation wavelengths, such as 495 nm, 590 nm, 685 nm, and 730 nm, using radiation-induced attenuation (RIA) analysing curves. The total dose values of 10 kGy and 50 kGy were studied to demonstrate the results under extreme environmental conditions such as large hadron colliders (LHCs). Our findings reveal that the formation of radiation-induced color centers (e.g. AlOHC, POHC, and NBOHC) are highly dependent on the Yb-concentration, the amount of excess alumina (Al 2 O 3 ) compared to the phosphorous pentoxide (P 2 O 5 ), total irradiation dose and wavelength at which the respective RIA is recorded.

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