Fabrication of waveguides in Foturan by femtosecond laser

We report two methods of fabricating waveguides in photosensitive Ag+ doped Foturan glass by femtosecond laser writing and subsequent annealing. The first method involves writing at laser energies higher than the optical breakdown threshold, directly resulting in microstructural changes and a refractive index increase. In contrast, the laser energy used in the second method was much lower than the threshold for optical breakdown. Subsequent thermal annealing at 500 °C after this writing process causes Ag nanoparticles to precipitate in the laser written trace and a corresponding increase in the refractive index. The effect of Ag nanoparticles population on the guiding characteristics of the written waveguides is addressed. We found that there is an optimum population of Ag nanoparticles in a waveguide. Propagation losses increase at above this population level due to high absorption/scattering, while a population level below the optimum is indicative of minimal index change and hence providing poor confinement.