REFRACTIVE INDEX CONTROL METHOD FOR QUARTZ OPTICAL WAVEGUIDE CORE GLASS

PROBLEM TO BE SOLVED: To enable the increase/decrease control of a refractive index through a simple facility and a method to be easily handled. SOLUTION: A core glass film 1, which is produced by low pressure plasma chemical vapor deposition(LP-CVD), to be sued for a quartz optical waveguide is arranged on a holder 6 in a vacuum chamber 2. The specified part of the core glass film is irradiated with the short wavelength ultraviolet light of wavelength 146 nm (the excimer light of krypton) or wavelength 172 nm (the excimer light of xenon) from an ultraviolet lamp 3 of low power density composed of an excimer lamp, for example, through an MgF2 window 5 so that the refractive index can be increased only at the specified irradiated part. By locally performing thermal anneal to the non-irradiated or irradiated part, the refractive index is reduced only at that part.