Optical waveguides and devices including same

摘要

A photosensitive glass made of a ternary compound SiO2:SnO2:R2O where R is a Group I element such as Na, K or Li. The addition of an oxide of a Group I element increases the solubility of tin oxide in a silica matrix and produces a glass which is highly photosensitive and in which optically written refractive index modulations have remarkable temperature stability (solid circles) at least as good as that of the binary glass SiO2:SnO2 (open circles) and much superior to that of conventional germanosilicate glass (solid triangles) or borogermanosilicate glass (open triangles). The inclusion of the Group I oxide effectively increases the solubility of tin oxide in the non-crystalline silica matrix well above the 1 % limit of SiO2:SnO2 photosensitive glass, at which Sn would normally crystallise in the oxide. By contrast to boron or phosphorous co-dopants, the introduction of the Group I element does not appear to cause any increase in the background refractive index, allowing the manufacture of waveguide devices compatible with standard telecommunication fibres.