Grating formation in a phosphorus-doped germanosilicate fiber

Summary form only given. To conclude, we have observed -5/spl times/10/sup -4/ index changes in a phosphorus-doped germanosilicate fiber and ready formation of Type IIa gratings in this fiber. Recently, an index change as high as 1/spl times/10/sup -4/ was reported in a telecommunication fiber at 193 nm, once again demonstrating the advantage of writing at this wavelength.