Graded refractive index glasses

A two-dimensional guide need not have a rectangular cross section or sharp boundaries. Glass fibers in which the refractive index decreases approximately in proportion to the square of the distance from the axis of the fiber are currently being developed for use in communication systems (14). Graded refractive-index distributions are used for this application because they... 

Step-index fibers are manufactured using the rod/tube or the double crucible process, in which the core and cladding glasses are melted separately from ultrapure powders and transferred into two crucibles with concentric orifices at the bottom and drawn into a fiber. To obtain a semi graded refractive index profile, a diffusion process can be applied in a curing furnace. Step index fibers with a transmission loss of < 10 dB/km at a wavelength of 0.8. pm can be obtained. 

Since the early stage of FGM research, many studies on the liquid phase method, such as sol-gel, electrodeposition, and plasma spray for the preparation of FGMs have been done because the liquid phase method is convenient and facilitates control of the graded composition. Cu/CuZn and Cu/CuNi FGM films with a thickness of 50-200 pm have been prepared on a Cu substrate by the electrodeposition technique [38]. A glass rod having a radially graded refractive index was... 

Poly(vinyl acetate) is too soft and shows excessive cold flow for use in moulded plastics. This is no doubt associated with the fact that the glass transition temperature of 28°C is little above the usual ambient temperatures and in fact in many places at various times the glass temperature may be the lower. It has a density of 1.19 g/cm and a refractive index of 1.47. Commercial polymers are atactic and, since they do not crystallise, transparent (if free from emulsifier). They are successfully used in emulsion paints, as adhesives for textiles, paper and wood, as a sizing material and as a permanent starch . A number of grades are supplied by manufacturers which differ in molecular weight and in the nature of comonomers (e.g. vinyl maleate) which are commonly used (see Section 14.4.4)... 

A similar deposition system uses a plasma which is produced by a traveling microwave cavity. No other source of heat is required. The deposition system is shown schematically in Fig. 16.12. The reactants are the same as in the thermal CVD process. Pressure is maintained at approximately 1 Torr. In this case, the deposition occurs at lower temperature, no soot is formed and a compact glass is produced directly. A main advantage of this method is the more accurate grading of the refractive index of the cladding material. 

Germanium dioxide has high refractive index and infrared transmission, for which it is used in industrial glasses. It also is used in preparation of high purity grade germanium. 

Cleaning of SPR glass slides (optical grade SF2, refractive index 1.65, from UQG Optical Components). Sonicator (e.g., Lucas Dawe sonication bath) and different solutions hydrochloric acid/nitric acid 3 1 v/v (solution A) ammonium cerium nitrate (1M) (solution B) sulfuric acid/hydrogen peroxide 1 1 (Piranha solution) isopropanol. Use caution in handling these solutions harmful and corrosive. 

Figure 7.9 Refractive index profiles of three common types of optical glass fiber multimode step index, multimode graded index, and single mode.

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