Low-dimensional materials, due to their versatile properties are very interesting for numerous electronics and optoelectronics applications. Recently rediscovered black phosphorus, with a graphite-like structure can be exfoliated up to the single atomic layer. In contrary to graphene it possesses a direct band gap controllable by the number of stacked atomic layers. For those reasons, it is now intensively investigated. Here we demonstrate, that black phosphorus can serve as a broadband saturable absorber and can be used for ultrashort optical pulse generation.The mechanically exfoliated ~300 nm thick layers of black phosphorus were transferred onto the fiber core and under pulsed excitation at 1560 nm wavelength its transmission increases by 4.4%.It was used to generate 272 fs-short pulses at 1550 nm and 739 fs at 1910 nm. The obtained results shows that black phosphorus can be effectively used for ultrashort pulse generation and proves its great potential to future applications.
We report, for the first time to our knowledge, the usage of black phosphorus (BP) as a saturable absorber for the mode locking of a thulium-doped fiber laser. We have experimentally shown that BP exhibits saturable absorption in the 2 μm wavelength range and supports ultrashort pulse generation. The saturable absorber was based on mechanically exfoliated BP deposited on a fiber connector tip. The laser was capable of generating 739 fs pulses centered at 1910 nm. Our results show that BP might be considered as a universal broadband saturable absorber that could successfully compete with graphene or other low-dimension nanomaterials.
In this letter we present for the first time, to the best of our knowledge, a harmonically mode-locked Er-doped fiber laser with antimony telluride (Sb2Te3) topological insulator material used as a saturable absorber (SA). The SA was prepared via mechanical exfoliation of the bulk material. The 80 nm thick Sb2Te3 layers transferred onto fiber ferrule entirely cover the fiber core. The Er-doped fiber mode-locked laser based on such SA generated optical pulses was centered at 1558 nm with 1.9 ps duration and a fundamental repetition rate of 3.75 MHz. Increasing the pump power results in stable harmonic mode-locked operation up to the 81st harmonic at 304 MHz repetition frequency. The laser was capable of generating optical solitons with 2.2 ps duration. The number of generated harmonics could be tuned only by changing the pump power injected into the laser cavity.
In this paper, femtosecond pulse generation in an Er-doped fiber laser is reported. The laser is passively mode-locked by an antimony telluride (Sb 2 Te 3 ) topological insulator (TI) saturable absorber (SA) placed on a side-polished fiber. The Sb 2 Te 3 /chitosan suspension used to prepare the SA was obtained via liquid phase exfoliation from bulk Sb 2 Te 3 .Ultra-short 449 fs soliton pulses were generated due to the interaction between the evanescent field propagated in the fiber cladding and the Sb 2 Te 3 layers. The optical spectrum is centered at 1556 nm with 6 nm of full-width at half maximum bandwidth. The presented method benefits from a much better repeatability compared to mechanical exfoliation.
This
study aimed to evaluate, for the first time, implantable,
biodegradable fiducial markers (FMs), which were designed for bimodal,
near-infrared fluorescence-based (NIRF) and X-ray-based imaging. The
developed FMs had poly(l-lactide-co-caprolactone)-based
core–shell structures made of radiopaque (core) and fluorescent
(shell) composites with a poly(l-lactide-co-caprolactone) matrix. The approved for human use contrast agents
were utilized as fillers. Indocyanine green was applied to the shell
material, whereas in the core materials, iohexol and barium sulfate
were compared. Moreover, the possibility of tailoring the stability
of the properties of the core materials by the addition of hydroxyapatite
(HAp) was examined. The performed in situ (porcine
tissue) and in vivo experiment (rat model) confirmed
that the developed FMs possessed pronounced contrasting properties
in NIRF and X-ray imaging. The presence of HAp improved the radiopacity
of FMs at the initial state. It was also proved that, in iohexol-containing
FMs, the presence of HAp slightly decreased the stability of contrasting
properties, while in BaSO4-containing ones, changes were
less pronounced. A comprehensive material analysis explaining the
differences in the stability of the contrasting properties was also
presented. The tissue response around the FMs with composite cores
was comparable to that of the FMs with a pristine polymeric core.
The developed composite FMs did not cause serious adverse effects
on the surrounding tissues even when irradiated in vivo. The developed FMs ensured good visibility for NIRF image-supported
tumor surgery and the following X-ray image-guided radiotherapy. Moreover,
this study replenishes a scanty report regarding similar biodegradable
composite materials with a high potential for application.
The article presents the comparative study of two metallization schemes, Ti/Al bilayer and Ti/Al/Mo/Au multilayer to AlGaN/GaN heterostructures. The influence of thermal annealing on the topography and sheet resistance Rsh of the metallization was investigated. At the temperature of annealing up to 805 °C Ti/Al metallization morphology changed but the metallization continuity was sufficient to obtain the sheet resistance below 2 Ω/□. Annealing at 820 °C caused the strong increase of sheet resistance up to 254 Ω/□. These results clearly indicated on very large heterogeneity of Ti/Al layers, material phase segregation, and the separation into individual islands. The annealing of Ti/Al/Mo/Au metallization also resulted in rise of sheet resistance. But the continuity of Ti/Al/Mo/Au layers did not deteriorate the sheet resistance value and homogeneity so significantly as for Ti/Al layers. In this case the changes were much lower, Rsh increased only to 1.15 Ω/□.
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