Amorphous xGeO<sub>2</sub>–(1-<i>x</i>)SiO<sub>2</sub> thin films exhibit large negative index changes (4–8%) in the high GeO<sub>2</sub> region (x>~0.25) on irradiation with ArF laser pulses. The sign of the index change is opposite the low GeO<sub>2</sub> region X<0.25, and the magnitude of the index change is larger by an order of magnitude than that reported so far. Cross-sectional transmission electron microscope observation has revealed that nanometer-scale phase separation is induced in these highly photosensitive glasses by irradiation with ArF excimer laser light pulses or electron beams. This is a first finding of microphase separation in SiO<sub>2</sub>–GeO<sub>2</sub> glasses by irradiation and provides an essential constraint on the modeling of photonic effects induced by irradiation in these glasses.
© 1999 Optical Society of America
(160.2750) Materials : Glass and other amorphous materials
(160.5320) Materials : Photorefractive materials
(310.3840) Thin films : Materials and process characterization
(350.3390) Other areas of optics : Laser materials processing
Hideo Hosono and Junji Nishii, "High photosensitivity and nanometer-scale phase separation in GeO2-SiO2 glass thin films," Opt. Lett. 24, 1352-1354 (1999)