Micromachined passive waveguide fabrication with fs laser in Ag-doped GeO₂–PbO glasses for photonics: straight, curved and Y shaped configurations

This study aims to produce and characterize different dual waveguides using femtosecond (fs) laser irradiation on GeO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>-based glass samples. The work is motivated by previous results obtained with rare earth ions doped GeO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> – PbO glass, with and without silver nanoparticles, in which irradiation, with fs laser was successful. The work aims to manufacture different structures such as straight, curved, and Y waveguides (using the double guide configuration) for applications in photonics (resonant rings, beam splitters, among others) in GeO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> – PbO glasses with silver nanoparticles. For both, straight and S curved waveguides, better M<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (beam quality factor) results were found for a distance between the guide walls of 10 μm, when compared to 25 μm. Moreover, among the two different curved guides produced it was also possible to observe better guidance when a larger radius of curvature (20 mm) was used; preliminary tests showed no guiding for 5 mm and 10 mm radius. The highest relative propagation loss was obtained for the S curved waveguide with a 25 μm distance between the guide walls whereas the lowest one was found for the Y shaped waveguide; for this configuration (opening angle of 5° and distance of 620 μm between the two arms) an output power ratio between the left and right arm of 53.9/46.1 showed promising applications for beam splitters.