Buried Depressed-Cladding Waveguides Fabricated in RE3+:CLNGG Laser Crystals using Direct Laser Writing Technique

For at least a decade now, direct writing with a femtosecond (fs) laser beam technique (FS-DLW) is employed for waveguide fabrication in various transparent optical materials [1]. This method makes use of an fs-laser beam to induce changes of the material's optical properties, these modifications being dependent on the medium's nature, on the fs-laser beam parameters, as well as on the focusing conditions [2]. For crystalline and ceramic materials, waveguiding is commonly realized in the volume confined between the written tracks (Type II waveguides), with double-wall or more complex structures. Among YAG and YVO
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crystals, laser gain media with partially disordered crystalline structure have been of great interest because they possess a unique combination of spectral and thermal properties [3–5]. They are a good candidate for generation of short and ultra-short laser pulses from compact structures, using passive Q-switch regime or mode-locking technique.