Correlation of the refractive index change at the surface and inside phosphate glass upon femtosecond laser irradiation
[EN] A study of the surface modification induced by single femtosecond laser pulses in phosphate glass has revealed surface swelling at fluences just below the ablation threshold. This behavior is different from that observed in other dielectric materials. Optical micrographs obtained with monochrom...
| Authors: | , , , , |
|---|---|
| Format: | article |
| Publication Date: | 2012 |
| Country: | España |
| Institution: | Universitat Politècnica de València (UPV) |
| Repository: | RiuNet. Repositorio Institucional de la Universitat Politécnica de Valéncia |
| Language: | English |
| OAI Identifier: | oai:riunet.upv.es:10251/28774 |
| Online Access: | https://riunet.upv.es/handle/10251/28774 |
| Access Level: | Open access |
| Keyword: | Ablation thresholds Bulk glass Fabry-Perot etalons Fluences Low density Monochromatic light Optical micrographs Phosphate glass Refractive index changes Surface layers Surface swelling Waveguide fabrication Waveguide writing Dielectric materials Refractive index Ultrafast lasers Waveguides Ultrashort pulses |
| Summary: | [EN] A study of the surface modification induced by single femtosecond laser pulses in phosphate glass has revealed surface swelling at fluences just below the ablation threshold. This behavior is different from that observed in other dielectric materials. Optical micrographs obtained with monochromatic light show a pattern of Newton rings within the swollen region whose number scales inversely with the illumination wavelength, acting as a micro Fabry-Perot etalon. The swollen surface layer has lower refractive index than the bulk glass and can reach a maximum thickness of 820 nm. We relate these findings to results obtained during subsurface waveguide writing inside phosphate glass, which also show a refractive index decrease at energies near threshold for waveguide fabrication. We have identified low density free-electron plasma to be the trigger of the refractive index change. © 2012 Optical Society of America. |
|---|