Refractive-index gratings written by near-ultraviolet radiation

This is the first report, to our knowledge, of refractive-index grating side writing in 10 mol. % GeO₂-doped fiber by the near-UV light of a cw ${\mathrm{Ar}}^{+}$ laser (333–364 nm). An induced-index magnitude as large as $1.9\times {10}^{-4}$ at $1.7\times {10}^5\mathrm{W}/{\mathrm{cm}}^2$ UV power density has been achieved. The observed gratings have exhibited the same temperature stability as gratings written by a KrF excimer laser (248 nm).