UV induced densification during Bragg grating inscription in Ge:SiO2 preforms: interferometric microscopy investigations

The only investigation of Bragg grating in Ge:SiO2 in the direct space known at this date is a view from an optical microscope. Here, we show surface level modulations associated with writing of grating. Our conclusion is that a densification takes place which corresponds to a refractive index increase. Compared to the refractive index change obtained by optical measurement, this accounts for a non-negligible part (7%).

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