Demonstration of Type A volume Bragg gratings inscribed with a femtosecond Gaussian-Bessel laser beam

our knowledge, we report on the first demonstration of Type A VBGs inscribed in silver-containing phosphate glasses by femtosecond laser writing. The gratings are inscribed plane-by-plane by scanning the voxel of a 1030 nm Gaussian-Bessel inscription beam. This results in a refractive-index modification zone, induced by the appearance of silver clusters, extending over a much larger depth than those obtained with standard Gaussian beams. As a result, a high diffraction efficiency of 95% at 632.8 nm is demonstrated for a 2-mu m period transmission grating with a 150-mu m effective thickness indicating a strong refractive-index modulation of 1.78 x 10-3. Meanwhile, a refractive-index modulation of 1.37 x 10-3 was observed at a wavelength of 1.55 mu m. Thus, this work opens the avenue for highly effective femtosecond-written VBGs suitable for industrial applications.(c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

In this work, the first demonstration of Type A volume Bragg gratings (VBGs) inscribed in silver-containing phosphate glasses by femtosecond laser writing is reported. The gratings are inscribed plane-by-plane using a 1030 nm Gaussian-Bessel inscription beam, resulting in a refractive-index modification zone induced by silver clusters. The highly effective femtosecond-written VBGs with strong refractive-index modulation have potential applications in various industrial sectors.