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Fibre Lasers
Published in Yu. N. Kulchin, Modern Optics and Photonics of Nano and Microsystems, 2018
The use of a composite configuration of stimulated Raman lasers makes it possible to create radiation sources that cover a spectral range of 1.6-1.75μm $ 1.6 - 1.75{{\mu m}} $ . To obtain laser radiation in the wavelength region near 2 μm or more, it is necessary to use optical fibres based on GeO2 $ {\text{GeO}}_{ 2} $ , since the glass containing germanium dioxide has minimum of losses in this region.
Optoelectronics – solid state optical devices
Published in David Jiles, Introduction to the Electronic Properties of Materials, 2017
Optical fibres are made from glass or plastic (‘plexiglass’ or ‘perspex’). These are solid tubes which act as waveguides for light. High quality optical fibres are made from glass as the attenuation is lower than for plastic fibres. The high attenuation of plastic fibres means that they are only used in a limited number of applications, usually for shorter-distance communications. The glass optical fibres are thinner than a human hair and consist of a core region with larger refractive index and an outer cladding region with lower refractive index. The refractive index of the material is changed using dopants such as germanium dioxide, phosphoric oxide or boric oxide. This arrangement confines the light to the core region. Core diameters are typically l–100μm in diameter, while the cladding is typically 100–300 μm in diameter.
Innumerable Biographies: A Brief History of the Field
Published in John D. Cressler, Silicon Earth, 2017
On December 8, Bardeen suggested they replace the silicon with (in retrospect) less defective germanium. They suddenly achieved an amplification of 330×, but unfortunately only at very low frequencies (rendering it unsuitable for the envisioned applications). Bardeen and Brattain thought the liquid might be the problem, and they then replaced it with germanium dioxide (GeO2). On December 12, Brattain began to insert the point-contacts. To his chagrin, nothing happened. In fact, the device worked as if there were no oxide layer at all. As Brattain poked the gold contact repeatedly, he realized that no oxide layer was present; he had washed it off by accident. Furious with himself, he serendipitously decided to go ahead and play a little with the point-contacts anyway. To his intense surprise, he again achieved a small amplification, but importantly, across all frequencies. Eureka! The gold contact was effectively puncturing the germanium and passivating the crystal surface, much as the water had.
Comment on “A review of public and environmental consequences of organic germanium” by Zheng and co-workers
Published in Critical Reviews in Environmental Science and Technology, 2023
First, in some scientific (and pseudo-scientific) communities, the use of the term stems from its use by K. Asai in the book “Miracle Cure. Organic Germanium,” published in 1980. The book, in addition to singing the praises of the therapeutic wonders of “organic germanium,” includes a chapter on “From the logical world of science to the mystic world of god.” Another book describing the benefits of “organic germanium” is “Germanium. The Health and Life Enhancer” (Goodman, 1988), which contains a chapter on “Esoteric and speculative aspects of organic germanium.” K. Asai describes the synthesis of his “organic germanium,” carboxyethyl germanium sesquioxide, also known as GE-132, propagermanium, proxigermanium, SK-818, 2-carboxyethylgermasesquioxane (IUPAC name: 3-[(2-carboxyethyl-oxogermyl)oxy-oxogermyl]propanoic acid). Other compounds also considered to be “organic germanium” are spirogermanium (IUPAC name: 3-(8,8-diethyl-2-aza-8-germaspiro[4.5]decan-2-yl)-N,N-dimethylpropan-1-amine), originally synthesized by Rice et al. (1974), and sanumgerman (potassium citrato-ascorbato-succinato-germanate). In addition to mentioning germanium sesquioxide and GE-132, the U.S. Food and Drug Administration import alert of germanium products (FDA Import Alert 54–07, 2019) lists other names (GE-OXY-132, Vitamin “O,” Pro-Oxygen, Nutrigel 132, Immune Multiple, Germax), that will probably fall into the category of “organic germanium.” From the chemical point of view, carboxyethyl germanium sesquioxide and spirogermanium are intrinsically different from sanumgerman; they are organometallic compounds. Organometallic compounds are chemical compounds that contain at least one chemical bond between a carbon atom of an organic molecule and a metal (IUPAC, 1977). Sanumgerman, even if it contains organic ligands, lacks direct metal-carbon bonds; it is a metal coordination complex of organic ligands. Many germanium organometallic compounds have been obtained by chemical synthesis and some are used in technological applications, like, for instance, tetramethylgermanium and tetraethylgermanium in the microelectronics industry as precursors for germanium dioxide chemical vapor deposition. In addition, two germanium organometallic compounds, methyl germanium and dimethyl germanium, have been found in oceans and freshwaters. Their source is considered to be natural, but is so far unknown (Lewis & Meyer, 1993); their concentrations in oceans are 1.5–26 ng L−1, depending on study; much lower in freshwaters (around 0.1 ng L−1). They are characterized by being very unreactive, thus leading to a conservative behavior in water bodies (Andreae & Froelich, 1984; Ellwood & Maher, 2003). In brief, this type of “organic” compounds, organometallic, irrespective of their origin—man-made or natural—are very persistent and are expected to remain in environmental compartments for a long time; however, as far as is known, concentrations are too low to be an environmental problem.