A Single-Frequency Linearly Polarized Fiber Laser Using a Newly Developed Heavily Tm3+-Doped Germanate Glass Fiber at 1.95 μm

A compact linearly polarized, low-noise, narrow-linewidth, single-frequency fiber laser at 1950nm is demonstrated. This compact fiber laser is based on a 21-mm-long homemade Tm3＋-doped germanate glass fiber. Over 100-mW stable continuous-wave single transverse and longitudinal mode lasing at 195Ohm are achieved. The measured relative intensity noise is less than -135dB/Hz at frequencies over 5 MHz. The signal-to-noise ratio of the laser is larger than 72dB, and the laser linewidth is less than 6kHz, while the obtained linear polarization extinction ratio is higher than 22 dB.

Gain properties of germanate glasses singly doped with Tm^(3+) and Ho^(3+) ions

Two kinds of germanate glasses singly doped with the ion concentration of 2.0mol.%Tm3＋ and 2.0mol.%Ho3＋, respectively, were prepared.According to McCumber theory, the absorption and stimulated emission cross-sections corresponding to the 3H6←→3F4 transitions of Tm3＋（at 1.8 μm） and the 5I8←→5I7 transitions of Ho3＋（at 2.0 μm） were obtained, and respective gain cross-section spectra were also computed as a function of population inversion according to absorption and emission cross-sections and the ion concentrations.For Tm3＋-doped germanate glasses, the maximum of the absorption, emission, and gain cross-sections reached a value higher than those reported for fluorozirconate, fluoride, and oxyfluoride glasses.For Ho3＋-doped germanate glasses, the maximum of absorption, emission, and gain cross-sections reached a value higher than that reported for fluorozircoaluminate glasses.Hence, these Tm3＋-doped and Ho3＋-doped germanate glasses exhibited an advantage for application in mid-infrared lasers at about 1.8 and 2.0 μm wavelength.

Bubble Generation in Germanate Glass Induced by Femtosecond Laser

We report the observation of bubble generation and migration in a germanate g/ass during irradiation by a femtosecond laser of high repetition rate. Bubbles are formed around the focal area of the laser beam, and their movement indicates the presence of thermal gravity convection in the glass melt, which is beyond the existing theoretical model about temperature l^eld of focal area. Inside the bubbles, oxygen molecules are observed by the con focal Raman micro-spectroscopy. The generation of molecular oxygen and bubbles is explained in terms of the spatial separation of Ge and 0 ions and micro-explosion inside the glass melt.

Layer Zirconogermanate——(H_2DETA)[ZrGe_3O_8F_2] Showing Odd 3MR and 7MR

A layered zirconogermanate, （H2DETA）[ZrGe3O8F2]（1）, was hydro（solvo）thermally synthesized with diethylenetriamine（DETA） as template, and structurally determined by X-ray single-crystal diffraction. Compound 1 crystallized in the monoclinic space group P21/c with data of unit cell： a=0.7644（2） nm, b=1.1235（2） nm, c=1.6860（3） nm, V=1.4479（5） nm^3,/a（Mo Ka）=6.931 mm^-1, Z=4, R1=0.0402 for 3236 reflections with Fo〉2σ（Fo）. The structure of compound I was formed by alternatively packing the inorganic layer of ZrGe3O8F2 and H2DETA templated molecules along （001） direction. It was worth pointing out that the odd bifurcated 7MR nets were surrounded by odd 3MR. The protonated and disordered H2DETA cations not only balanced the superfluous charges of framework but also stabilized the structure of compound 1 by the hydrogen bond between -NH3 group and oxygen on the framework. Furthermore, IR and TG were utilized to characterize the structure and thermal stability, respectively.

Radiation resistance property of barium gallo-germanate glass doped by Nb_(2)O_(5)

Effects of Nb_(2)O_(5)dopant on the radiation response of barium gallo-germanate(BGG)glass are studied mainly by electron paramagnetic resonance and absorption spectroscopy.Owing to the Nb^(5+)$Nb^(3+)interconversion in doped samples,formations of Ge-related non-bridging oxygen hole center and Ge-related electron center defects after g-ray irradiation are inhibited.Thereby,Nb_(2)O_(5)dopant can enhance radiation resistance of BGG glass,and 1.0%Nb2O5 concentration is the best.

Sol gel Synthesis and Hydrothermal Crystallization of Gallium Germanate

A novel gallium germanate (83/2 Na2O . 1/2 Ga2O3 . 24 GeO2) was synthsized by a sol-gel method and hydrothermal crystallization. The germanate was characterized with scanning electron microscopy, electronic energy spectrum, inductively couple plasma-emission spectrum and powder X-ray diffraction. The properties of crystal appearance, size, thermal stability and melting point were studied as well as some influence factors on synthesis process.

Sol-gel Synthesis and Hydrothermal Crystallization of Indium Germanate

A novel indium germanate (183/2Na 2O·1/2In 2O 3·28GeO 2) was synthesized by a sol gel and hydrothermal crystallization. The germanate was characterized with scanning electronic microscopy, electronic energy spectrum, inductively couple plasma emission spectrum and powder X ray diffraction. The properties on its crystal appearance, size, thermal stability and melting point, and some influent factors on synthesis were studied.

Highly efficient,tunable,ultrabroadband NIR photoemission from Bi-doped nitridated germanate glasses toward all-band amplification in optical communication

Bismuth(Bi)-doped near-infared(NIR)glass that can cover the entire optical communication window(850,1310,and1550 nm)has become the subject of extensive research for developing photonic devices,particularly,tunable fiber lasers and ultrabroadband optical amplifiers.However,the realization of highly efficient NIR luminescence from Bi-doped glass is still full of challenges.Notably,due to the co-existence of multiple Bi NIR centers in the glass,the origin of newly generated Bi NIR emission peaks at~930 and~1520 nm is still controversial.Here,we report a new Bi-doped nitridated germanate glass with tunable ultrabroadband NIR emission(850–1700 nm)and high external quantum efficiency(EQE)of~50%.A series of studies,including spectral analysis,nuclear magnetic resonance(NMR),and others,provide powerful evidence for the mechanism of luminescence enhancement and tunability,and make reasonable inferences about the origin of the new emission bands at~930 and~1520 nm.We believe that the results discussed above would enrich our understanding about multiple Bi NIR emission behaviors and contribute to the design and fabrication of highly efficient Bi-doped ultrabroadband wavelength-tunable optical glass fiber amplifiers and lasers in the future.

Emission enhancement in Er^(3+)/Pr^(3+)-codoped germanate glasses and their use as a 2.7-μm laser material

Emission enhancement at 2.7 μm is observed in Er^3＋/Pr^3＋--codoped germanate glasses when pumped by a 980-nm laser diode. Significant reductions in 1.5-μm emission and upeonversion intensity indicate efficient energy transfer between Er^3＋ and Pr^3＋; the energy transfer efficiency is as high as 77.4%. The mechanisms of energy transfer are discussed in detail. The calculated emission cross-section of Er^3＋/Pr^3＋- codoped germanate glass is 8.44× 10 ^-21 cm^2, which suggests that Er^3＋/Pr^3＋-codoped germanate glass can be used to achieve efficient 2.7-μm emission.

Bismuth-doped germanate glass fiber fabricated by the rod-in-tube technique

Bismuth （Bi）-doped laser glasses and fiber devices have aroused wide attentions due to their unique potential to work in the new spectral range of 1 to 1.8 μm traditional laser ions, such as rare earth, cannot reach. Current Bi-dopcd silica glass fibers have to be made by modified chemical vapor deposition at a temperature higher than 2000℃. This unavoidably leads to the tremendous loss of Bi by evaporation, since the temperature is several hundred degrees Celsius higher than the Bi boiling temperature, and, therefore, trace Bi （-50 ppm） resides within the final product of silica fiber. So, the gain of such fiber is usually extremely low. One of the solutions is to make the fibers at a temperature much lower than the boiling temperature of Bi. The challenge for this is to find a lower melting point glass, which can stabilize Bi in the near infrared emission center and, meanwhile, does not lose glass transparency during fiber fabrication. None of previously reported Bi-doped multicomponent glasses can meet the prerequisite. Here, we, after hundreds of trials on optimization over glass components, activator content, melting temperature, etc., find a novel Bi-doped gallogermanate glass, which shows good tolerance to thermal impact and can accommodate a higher content of Bi. Consequently, we successfully manu- facture the germanate fiber by a rod-in-tube technique at 850℃. The fiber exhibits similar luminescence to the bulk glass, and it shows saturated absorption at 808 nm rather than 980 nm as the incident power becomes higher than 4 W. Amplified spontaneous emissions are observed upon the pumps of either 980 or 1064 nm from ger- manate fiber.

Ambroxol,the cough expectorant with neuroprotective effects

Ambroxol hydrochloride(2-amino-3,5-dibromo-N-methylbenzylamine hydrochloride)has been used as a mucolytic agent in the treatment of respiratory diseases since the late 1970s.Its effects on mucus membranes such as mucus disruption,increased mucus production,and low toxicity profile were addressed in its original German patent in 1966.These first described properties have kept Ambroxol available worldwide and over the counter in the pharmaceutical market to this day.

German Überzeugt in China

In this exclusive interview,Michael Schumann,chairman of the Board of the German Federal Association for Economic Development and Foreign Trade,discusses Sino-German trade relations and the“out-of-proportion”debate on Xinjiang.

Two tetravalent uranium silicate and germanate crystals with three membered single-ring by molten salt method:K_(2)USi_(3)O_(9)and Cs_(2)UGe_(3)O_(9)

Two tetravalent uranium silicate and germanate M_(2)U^(Ⅳ)T_(3)O_(9)(M=K,Cs;T=Si,Ge)crystals were crystalized under inert gas by molten salt flux growth method.K_(2)USi_(3)O_(9)(1)crystallizes in the monoclinic space group P1_(21)/n1 with lattice parameters a=7.1076?,b=10.4776?,c=12.2957?,γ=120°and V=915.67?^(3).Cs_(2)UGe_(3)O_(9)(2)crystallizes in a hexagonal space group P-6 with lattice constants of a=7.5138?,b=7.5138?,c=11.0114?,γ=120°and V=538.38?^(3).Bond valence calculations indicate tetravalent uranium in both structures,which contain three-membered single-ring T_(3)O_(9)^(6-) trimers.K_(2)USi_(3)O_(9) is the first uranium silicate that contains the Si_(3)O_(9)^(6-) trimers.

Barium Gallogermanate Glass Ceramics for Infrared Applications

The germanate glass ceramics is a potential candidate material for infrared （IR） dome and window applications. The crystallization mechanism of 20BaO-10Ga2O3-70GeO2 glass was investigated by differential thermal analysis （DTA）, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Two different types of phase evolution were found in the early stage of crystallization： （1） the further growth of the microcrystal formed during the slow cooling of glass melt and （2） the glass-in-glass phase separation. The controlled crystatlization was obtained by two-step heat treatment. obtained, with expected thermal and mechanical The middle infrared （MIR）-transparent glass ceramics were improvements.

Self-starting harmonic mode-locked Tm-Bi co-doped germanate f iber laser with carbon nanotube-based saturable absorber

We report a ring cavity passively harmonic mode-locked fiber laser using a newly developed thulium- bismuth co-doped fiber （TBF） as a gain medium in conjunction with a carbon nanotube （CNT）-based saturable absorber. The TBF laser generates a third harmonic mode-locked soliton pulse train with a high repetition rate of 50 MHz and a pulse duration of 1.86 ps. The laser operates at 1 901.6 nm with an average power of 6.6 mW, corresponding to a pulse energy of 0.132 nJ, at a 1 552 nm pump power of 723.3 roW.

Artificial intelligence in ophthalmology

Immediate Past President of International Council of Ophthalmology(ICO);Academician and former Secretary General of Academia Ophthalmologica Internationalis(AOI);Former Chairman of the Scientific Program of the World Congress of Ophthalmology(WOC);Member of the German Academy of Sciences,former President of German Society of Ophthalmology(DOG);Former Executive Vice President of University of Leipzig and Director of the Eye Hospital;Member of the Club Jules Gonin Executive Committee(2000-2006)。

Silent Earth:Averting the Insect Apocalypse by Dave Goulson

There is well-documented evidence for an ongoing decline in flying insect biomass.The author briefly summarizes the 26-years of Malaise trap data(Hallmann et al.2017) from German nature reserves.An additional 10-year sweep-net study published by Seibold et al.(2019) found an even greater decline in insects on German forests and grasslands.Additional studies are cited that involve a variety of sampling methods and target butterflies,moths,aphids and other insects.Some studies go back to 1968.The results show declines of 28 to 46 percent.

German Landscape Development and Characteristics Analysis and Study:A Case Study of 20^(th)Century German Garden Landscape Design

Germany has a significant influence on the globe,both economically and culturally,being the center of Europe.Although severely damaged by the Second World War,German landscape architecture gradual y recovered through garden exhibitions,landscape associations,and other means during a period of reflection and repair.Because of their artistry and utility,German gardens from the middle and end of the 20^(th)century had a favorable influence on landscape architecture around the globe.The shift in focus from“post-war restoration”to“enhancing the urban appearance”to“ecological restoration”not only reflects a shift in the design philosophy of the German people but also directly reflects the value orientation of design across all of Europe and even the West.

Wisdom and Geology, the North German Basin, and the Significance of Thrown Dices

For thousands of years, mankind is observing the surrounding nature. Often, they found no obvious clues for inexplicable and complex facts, leading to the belief that their wisdom was limited. This is in the majority of cases still true today, but based on hundreds of years of (geo-) scientific work some older thoughts can now be readjusted by combining newer geological, environmental, historical and philosophical clues. Facts about the development of the North German Basin are used to demonstrate the variability of geological systems and how these can be described by taking dice as a metaphor for ruling geological parameters. This includes all kinds of plate tectonically controlled basin forming processes, especially metamorphism of the lower crust due to a fixed mantle plume, basin filling processes with their galactic and lunar overprints, basin modifying tectonics due to internal (halokinesis, inversion) or external forces (one-sided loads at the surface due to mighty Delta sediments or glacial ice sheets) and geochemical reactions as a result of pressure and temperature changes in course of subsidence. Especially, the Rotliegend (Lower Permian) Gas Play is one of the possible illustrations of the entity of the North German Basin with its more than 70 - 90 independent parameters belonging to a global set of very complex hydrocarbon systems. Processes on Earth like the formation of systems of hydrocarbon fields as well as environmental systems (e.g. river systems, lakes, islands, sedimentary basins) are subordinated to the dices of nature and are steered invisibly by a selection of rules of the game that one understands as natural laws. The facts and remaining uncertainties as well as problems with subsurface-related processes (e.g. manmade tectonics, subsidence and uplift) guide the thoughts of engaged individuals on how to proceed wisely with limited predictability of challenges and dangers of a subsurface system. This work will be a trial to associate once more the natural sciences (geology) and the humanities (philosophy) for the benefit of both.

Exploring Cultural Beauty of China’s Ethnic Groups

The goal of German young man Robert Adolf is to shoot short videos showing the culture of all 56 ethnic groups in China.NOT many know that the huge population of China is made up of 56 ethnic groups.All of these groups have their own customs,architecture,clothing,and festivals,which are so attractive to foreigners like Robert Adolf,a post-90s German young man who came to China after his graduation in 2017.