Thermodynamics of fluorine incorporation into silica glass

Fluorine Containing High-Silica Glasses for Speciality Optical Fibers

“…dopant concentration in the MCVD process can be well decribed as a rule by the chemical thermodynamics of the species taking part in the deposition reactions, this means by chemical equilibria between the gaseous and condensed (liquid or solid) phase, where the condensed glassy phase is considered as an ideal mixture of the components. This was earlier shown for germanium, phosphorus and boron incorporation [6,11,7] and recently also for the fluorine incorporation [4], where the thermodynamic potentials of the species were derived from a series of experiments with different fluorine sources. During the MCVD deposition at temperatures near 2000 K and with oxygen excess in the gas phase, the starting raw gases SiCl 4 and BBr 3 are fully converted to the oxides…”

“…The initial gas phase conditions are specified by the total gas flow V (in sccm = standard cubic centimeters per minute) and the molar fractions of the respective compounds X SiCl4 , X SiF4 , X GeCl4 , X BBr3 and X O2. Further details of the process are described in [4]. The refractive index of the deposited layers in the perform core was determined by a nondestructive beam deviation method [9].…”

“…However, there is a lack of knowledge regarding the interplay of two or more dopants during the preform and fiber preparation process. Recently, we have shown that the incorporation of fluorine into the preform and fiber core via gas phase deposition can be understood on the basis of chemical thermodynamics of the deposition process [4]. In the present study, we investigated the codoping of different high-silica glasses (GeO 2 -SiO 2 , B 2 O 3 -SiO 2 ) with fluorine.…”

“…In earlier papers, the incorporation of germanium and boron alone has been investigated and interpreted by a thermodynamical model [6,7]. On the basis of these results and taking into account the mechanism of fluorine incorporation [4], here we have calculated the chemistry for the codoping of silica with germaniun/fluorine and boron/fluorine, respectively. The main object of the paper presented here is to demonstrate, that the equilibrium chemistry approach, which is valid for the description of the singly doped systems, can be successfully applied even for the codoped systems GeO 2 -F -SiO 2 and B 2 O 3 -F -SiO 2 .…”

Chemically modified optical fibers in advanced technology: An overview

“…But for the case of OVD and VAD processes, the layer deposited on the outside of a rotating mandrel by using the flame hydrolysis. These methods are different in terms of deposition rate, efficiency and precision of refractive index profiles [35]. Particularly, MCVD process is a most common method for passive and active modification of OFs [36].…”