Search

The impact of thermal quenching on the photostability of bismuth active center (BAC) is investigated through measuring the photo-bleaching process under 830 nm irradiation in quenched Bi/Er co-doped fiber (BEDF). By fitting with the stretched-exponential model, the emission intensity ascribed to the photostable BAC associated with silica (BAC-Si) at 1400 nm (I( $\infty $ )), unbleachable ratio $(\gamma _{\textrm {UB}})$ and bleaching time $(\tau _{\mathbf {B}})$ are obtained. Compared to the untreated sample, the $\text{I}(\infty) $ increases with higher temperature or a longer dwell time, while both the $\gamma _{\textrm {UB}}$ and $\tau _{\mathbf {B}}$ decrease. The results show that BAC-Si could be bleached faster, while additional amount of BAC-Si could be retained in thermally quenched samples. Besides, the lower photostability of the newly quenching activated BAC, impacted by different quenching conditions, is estimated.

Bismuth-doped optical fiber (BDF) and bismuth/erbium co-doped optical fiber (BEDF) have attracted much attention due to their ultra-broadband luminescence in the near-infrared (NIR) region. The photobleaching effect on bismuth active centers (BACs) related to the NIR luminescence has been systematically investigated and summarized, in terms of irradiation intensity, irradiation wavelength, and temperature. All these findings not only give the deep insights into the fundamental structure of BACs but also provide an effective way to control the BACs. They play an important role for the development of BDF- and BEDF-based devices with high performance and stability under laser exposure in future.

Background This research was performed to investigate the effects of Pulsatilla Koreana NAKAI pharmacopuncture (PPA) therapy on intestinal disease in rats with dextran sulfate sodium (DSS)-induced colitis. Methods The subjects were divided into five groups : A control group, saline group, pharmacopuncture group PPA1 (0.2 ㎎/ 1 kg/ 40 ㎕), pharmacopuncture group PPA2 (0.5 ㎎/ 1 kg/ 40 ㎕), and pharmacopuncture group PPA 3(1 ㎎/ 1 kg/ 40 ㎕). The experimental model of colitis was induced by infection of dextran sulfate sodium (DSS) for eighteen days. After colitis was induced, PPA therapy was practiced on the Chunchu (ST25) once every two days for a total six times. Thereafter Disease Activity Index (DAI), colon length, damage to the colonic mucosa, body weight, IL-6, IL-10, IL-1β, IFN-γ, TNF-α, TGF-β1, IL-23 and IL-17 were measured. Results The results were as follows. 1. DAI was significantly decreased in the PPA groups. 2. Colon length was significantly increased in the PPA groups. 3. Damage of colonic mucosa was observed less in the PPA groups. 4. Body weight was significantly increased in the saline group and the PPA groups. 5. The PPA2 group showed a significant decrease in the intensity of IL-6, IL-1β, IFN-γand TNF-α levels and the mean of IL-23. 6. The PPA3 group showed a significant increase in the intensity of IL-10 and TGF-β1 levels. 7. No significant differences were shown in the mean of IL-17. Conclusions These results suggest that PPA therapy on Chunchu (ST25) can be used as an effective treatment for inflammatory bowel disease.

Bismuth active center associated with silica (BAC-Si) activation and thermal darkening effect at high temperature has been distinguished in a bismuth/erbium co-doped fiber (BEDF). Activation could be achieved ahead of the severe thermal darkening effect.

The photostability of bismuth active centre associated with aluminium (BAC-Al) and bismuth active centre associated with silicon (BAC-Si) in bismuth/erbium co-doped optical fibre (BEDF) is investigated at a wide range of laser wavelengths. © 2020 The Author(s)

The thermal treatment effect on bismuth active center associated with aluminum (BACAl) has been investigated. The results indicate that thermal treatment leads to significant degradation of BAC-Al in 3D printed bismuth/erbium co-doped optical fibre. © 2019 The Author(s)

State-of-the-art optical fiber communication system reaches to transmission capacity from tens to hundreds of Tb/s. The massive capacity crunch has sparked concerns regarding available bandwidth and constantly increasing optical data traffic. Certainly, one way is to broaden the spectral transmission range beyond the narrow gain band of current erbium doped fiber amplifier (EDFA). Either side of Erbium across low-loss transmission window (1.5μm) shown promising results with optical fibres codoped with rare-earth-doped materials such as bismuth/thulium. Hence, it is of crucial importance to develop broadband optical amplifier to fully utilize the uncovered spectral regions with proper choice of pump wavelength(s)/Laser diodes. Here we have compared the performances of Bismuth/Erbium and Ytterbium/Erbium co-doped fibres as pumped to 808nm to one as pumped at 830nm. The pumping excitation conditions and spectral characteristics in BEDF and EYDF are explored to maximize the lasing efficiency. Using equivalent conditions and same section of Bi/Er codoped fiber, an enhanced broadband emission with FWHM ~ 149 nm is observed in Bi active centers (BAC) related to Si around ~1420nm under 808nm excitation as compared to 830nm with its FWHM ~ 125nm at an input power of ~ 55.5 mW. At maximum power, under 808nm pumping, a well-known peak emission of Er3+ at 1536nm noticeably increased due to reabsorption of BAC-Si (~1420nn) with the ratio ~ 1.7 between Er3+ and BAC-Si emission peaks. On the contrary, emission peak of the BAC-Si revealed higher with the ratio of ~ 1.5 than that of Er3+ by 830nm pumping. Afterward, we observed Yb3+ emission at 1040nm and 980 nm using Yb/Er codoped fiber with both pumps at same power. Using 808nm pumping, an extended emission band around ~ 1230 nm appeared namely BAC-Al while the other emission bands associated with BAC-Si (~ 1480nm) and Er3+ (~1536nm) shown similar emission bands with high emission peaks compared to 830nm pump at equivalent pump powers. Furthermore, the emission peak of the BAC-Si is about the same level as that of Er3+ with ratio of RBi/Er~ 1.1 under 808nm pumping while 830 nm pump showed the ~ 5.25 ratio between the emission peaks of BAC-Si and Er3+. We believe that this side-by-side comparison of two pumps and two home-made fabricated codoped fibres could be useful as a promising strategy for the next-generation WDM passive optical networks employing single broadband amplifier and tunable fiber laser covering 1000-1800nm telecommunication bands.

We investigated thermal effect on attenuation and luminescence of Bi/Er co-doped fiber (BEDF). A strong and irreversible thermal darkening effect in both near-infrared (NIR) and visible spectral range was observed, accompanied by a luminescence quenching of bismuth active centers (BACs), in temperature range from 600 °C to 800 °C. This thermal darkening effect is believed to be linked to the precipitation of metallic bismuth nanoparticles and takes place at a relatively low temperature. We also observed that the quenching of BAC-Si in the BEDF is more prominent than other BACs. The BAC-Si related emission at 1420 nm is decreased by 80% when the temperature is increased to 600 °C—before the significant thermal darkening occurs and while the quenching of others BACs is not significant.

Bismuth/erbium co-doped optical fiber fabricated through 3D silica lithography is thermally treated with various conditions. Then the thermal treatment effect on bismuth active centers (BACs) in this fiber is investigated. The thermal bleaching of the BAC associated with Al and the BAC associated with Si is observed after thermal treatment at high temperatures (300°C–800°C). It is found that the absorption and luminescence of BACs dramatically decrease after the thermal treatment, even totally bleaching at 700°C. The results show that the temperature and dwell time have significant effects on the thermal bleaching and activation of BACs. The underlying mechanisms of these thermal-induced effects are further discussed.

Objectives : Herba on lipid levels in serum and lipid accumulation in liver tissue in high fat diet-induced hyperlipidemic mice. Methods : Experimental groups were subdivided into four; Normal diet group (Nor), Hyperlipidemic mice (Con), Lysimachiae Herba water extract administered mice (LWE), Lysimachiae Herba methanol extract administered mice (LME). Thereafter the changes in body weight, total cholesterol, LDL-cholesterol, HDL-cholesterol, triglyceride, AST, ALT, fasting blood glucose in serum were measured. In addition histopathological changes in liver tissue was also observed. Results : Body weight, AST and ALT were not affected by the administration of water or methanol extracts of Lysimachiae Herba. However, methanol extracts of Lysimachiae Herba down regulated the total cholesterol and triglyceride in high fat diet - induced hyperlipidemic mice. Conclusions : In this study, results of total cholesterol and triglyceride showed significant effect in LME compared with LWE, but other results didn’t. Therefore, it is necessary to have more study of Lysimachiae Herba to apply hyperlipidemia.

The thermal activation of the bismuth active center associated with silicon (BAC-Si) in bismuth/erbium-codoped optical fiber (BEDF) has been investigated in terms of temperature, dwell time, and cooling rate. The experimental results show that temperature and dwell time have significant effects on activation of BAC-Si, and the underlying mechanism is further discussed. Especially, through the optimization of these dynamic parameters, the thermal activation of BAC-Si is achieved with a maximum enhancement ∼ 2.5 times of peak luminescence intensity and 1.6 dB/m increment of the on–off gain at ∼ 1405 n m . Such discovery clearly indicates that thermal treatment with optimized temperature, dwell time, and cooling rate could be an effective way to activate BAC-Si in BEDF.

The thermal effect upon the photo-bleaching of bismuth/erbium co-doped optical fiber (BEDF) containing Al has been investigated. The photo-bleaching effects of aluminum related bismuth active center (BAC-Al) in BEDF are studied from room temperature (RT) up to 350°C under the irradiation of a 980 nm laser. No visible bleaching of the luminescence associated with BAC-Al was observed at RT, but significant bleaching appeared at higher temperatures above 150°C under the same irradiation power. The underlying mechanism of significant thermal aggravation of photo-bleaching is discussed, and its impact needs to be considered in the design and application of optical amplifiers and lasers using Al-doped BEDF.

We have investigated the thermal quenching effect on the bismuth active center (BAC) in a Bi/Er co-doped fiber (BEDF). The effects from varying quenching conditions are studied and discussed. We report, for the first time to our knowledge, a significant BAC activation achieved by thermal quenching. We observed that the peak luminescence at ∼1405 nm of the BAC associated with silica (BAC-Si) could be enhanced more than two times by thermal quenching. The experimental results indicate that thermal quenching could be an effective way for BAC activation of bismuth-doped fibers.

The unsaturable absorption and excited state absorption (ESA) for bismuth/erbium codoped fibers have been investigated under 830 nm pumping. The ESA and unsaturable absorption at 1050 nm are found to increase with increasing BAC-Al absorption.

We observed a reversible photo-bleaching effect in Bi/Er co-doped optical fiber. The bismuth related luminescence could be partially bleached by the irradiation of 830 nm pump, and recovered to original level after stopping irradiation.

We observed photo-bleaching in a bismuth/erbium co-doped optical fiber (BEDF) under 830 nm irradiation. As a result of the photo-bleaching, the absorption at 814 nm and the near-infrared luminescence at 1420 nm are decreased, indicating that the silicon-based bismuth active center (BAC-Si) in a BEDF is bleached in the process. We further found that the photo-bleaching is reversible under room temperature. This is the first time that the BAC-Si could be bleached under 830 nm irradiation, and the photo-bleaching is reversible. The underlying mechanism of the reversible photo-bleaching effect is discussed.

The electron paramagnetic resonance (EPR) parameters D, aandg for Fe 3+ ions in α-LiIO3 crystals are calculated on the basis of a microscopic crystal-field theory. In the calculation the contributions of the Li +-vacancies in the vicinity of Fe 3+ ions and the changes of the cation-ligand bond lengths are taken into consideration. The results calculated agree with experimental data. Our investigation shows that the local structure around the Fe 3+ ions possesses a compressed trigonal symmetry. This is unlike the host crystal in which the local structure is elongated. The bond angle Θ for the (FeO6) 9− group in α-LiIO3:Fe 3+ crystal is found to be greater than that of the host crystal by 5.78∘.

The spin–orbit and crystal-field matrices of d4,6 configuration with C3v symmetry are derived based on the weak-field scheme. Utilizing these matrices obtained and the approximate SCF d-orbit of Fe2+ proposed by Zhao, the zero-field splitting, optical absorption bands, and the Zeeman dependences are calculated for RbFeCl3. The calculation results agree well with experimental findings. Es werden die Spin–Bahn- und Kristallfeldmatrizen der d4,6-Konfiguration mit C3v-Symmetrie auf der Basis des schwachen Feldes abgeleitet. Mit diesen so erhaltenen Matrizen und den genaherten SCF-d-Funktionen von Fe2+, die von Zhao vorgeschlagen wurden, werden Nullfeld-Aufspaltung, optische Absorptionsbanden und die Zeemanabhangigkeiten fur RbFeCl3 berechnet. Die Rechnungsergebnisse stimmen gut mit den experimentellen Werten uberein.

The photo-stability of bismuth active center associate with silica (BAC-Si) in thermally-quenched Bi/Er co-doped fibers (BEDFs) indicates the slower quenching speed hardly affect the proportion of photo-stable BAC but accelerate the photo-bleaching of unstable BAC.

Through the topological engineering, Bi/Er/Yb co-doped optical fibre with the emission spectrum of an ultrabroad bandwidth of 692 nm and a high flatness of 0.611 has been predicted and designed. © 2020 The Author(s)

The annealing effects on bismuth active centers (BACs) in Bismuth/Erbium co-Doped Fiber (BEDF) have been investigated. We observed that annealing affects significantly the absorption and emission characteristics of the BACs, especially BAC-Si, in the BEDF.