Abstract
Laser-induced space-selective crystallization of glass enabling the growth of continuous crystal-in-glass architectures consisting of non-centrosymmetric phases with functional properties is promising, including single-crystal waveguides for the development of integrated optical circuits. In this study, femtosecond laser direct writing of crystalline lines inside lead germanate glass with the composition close to Pb5Ge3O11 has been demonstrated. The growth of crystalline lines by the .moving focused laser beam required the preliminary growth of a seed crystal by the fixed beam. Confocal Raman spectroscopy revealed the precipitation of ferroelectric Pb5Ge3O11, which, under certain exposure conditions, could be accompanied by precipitation of the metastable lead germanate phase. Depending on the laser beam parameters, either bilateral growth providing split, horseshoe-shaped morphology of the crystal cross-section, or centered growth resulting in elongated, elliptical cross-section shape occurred. The obtained results are of interest for the fabrication of ferroelectric Pb5Ge3O11-based crystal-in-glass waveguides.
Highlights
Controlled crystallization of glasses providing surface or bulk precipitation of functional crystalline phases is a well-known method for the development of novel functional materials [1]
We investigated the possibility and conditions of space-selective crystallization of lead germanate glass similar to the ferroelectric Pb5 Ge3 O11 phase in chemical composition by the femtosecond laser beam and analyzed the phases precipitated under the laser exposure by confocal Raman spectroscopy
The growth of crystalline lines by the moving focused laser beam required the preliminary growth of a seed crystal by the fixed beam
Summary
Controlled crystallization of glasses providing surface or bulk precipitation of functional crystalline phases is a well-known method for the development of novel functional materials [1]. In the two recent decades, progress in laser technology and laser-assisted microfabrication methods gave rise to numerous studies of laser-induced space-selective crystallization of glass and growth of crystalline architectures in glass by direct laser writing, which have been recently reviewed by Komatsu and Honma [2]. These methods open the way to the fabrication of 2D and 3D components of integrated optical circuits in glass matrix which obtain functional properties of crystals such as high second-order susceptibility, linear electrooptic effect, ferroelectricity, etc. Femtosecond-laser direct writing (FLDW) enables the fabrication of 3D crystalline architectures in the inside of glasses including continuous single-crystal tracks with waveguiding properties [4,5]
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