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Proceedings Paper

In-volume waveguides by fs-laser direct writing in rare-earth-doped fluoride glass and phosphate glass
Author(s): D. Esser; D. Wortmann; J. Gottmann
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Paper Abstract

Refractive index modifications are fabricated in the volume of rare-earth-doped glass materials namely Er- and Pr-doped ZBLAN (a fluoride glass consisting of ZrF4, BaF2, LaF3, AlF3, NaF), an Er-doped nano-crystalline glass-ceramic and Yb- and Er-doped phosphate glass IOG. Femtosecond laser radiation (τ=500fs, λ=1045nm, f=0.1-5MHz) from an Ybfiber laser is focused with a microscope objective in the volume of the glass materials and scanned below the surface with different scan velocities and pulse energies. Non-linear absorption processes like multiphoton- and avalanche absorption lead to localized density changes and the formation of color centers. The refractive index change is localized to the focal volume of the laser radiation and therefore, a precise control of the modified volume is possible. The width of the written structures is analyzed by transmission light microscopy and additionally with the quantitative phase microscopy (QPm) software to determine the refractive index distribution perpendicular to a waveguide. Structures larger than 50μm in width are generated at high repetition rates due to heat accumulation effects. In addition, the fabricated waveguides are investigated by far-field measurements of the guided light to determine their numerical apertures. Using interference microscopy the refractive index distribution of waveguide cross-sections in phosphate glass IOG is determined. Several regions with an alternating refractive index change are observed whose size depend on the applied pulse energies and scan velocities.

Paper Details

Date Published: 24 February 2009
PDF: 9 pages
Proc. SPIE 7205, Advanced Fabrication Technologies for Micro/Nano Optics and Photonics II, 720510 (24 February 2009); doi: 10.1117/12.808736
Show Author Affiliations
D. Esser, RWTH Aachen Univ. (Germany)
D. Wortmann, RWTH Aachen Univ. (Germany)
J. Gottmann, RWTH Aachen Univ. (Germany)

Published in SPIE Proceedings Vol. 7205:
Advanced Fabrication Technologies for Micro/Nano Optics and Photonics II
Thomas J. Suleski; Winston V. Schoenfeld; Jian Jim Wang, Editor(s)

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