Gradient And Core-Cladding Waveguides Fabrication In Porous Glass

We report on waveguides laser writing inside porous glass. Depending on applied laser regimes, two types of waveguides are fabricated in the same glass sample. A gradient waveguide type is achieved under the lowest pulse energy regime, which results in gradual densification of a nanoporous framework forming a core with an increased refractive index. The surrounding unirradiated material acts as a cladding. The highest pulse energy applied enables formation of the densified core surrounded by rarefaction regions in the nanoporous framework - a core-cladding waveguide type. Laser light guiding is also accomplished for both types to estimate the refractive index contrast. In addition, we determine the temperature distribution based on the thermal conduction model to reveal the difference of temperature gradients for the regimes applied.