Femtosecond laser processing in magneto-optical glasses

Qiang Liu*, Simon Gross, M. J. Withford, M. J. Steel

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

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Femtosecond laser direct writing (FLDW) is developing rapidly but to date, there is no native optical isolator (needed to mitigate reflections in any optical system) for the platform. As a step towards integrated glass isolators, we have investigated FLDW in kHz and MHz pulse rate regimes for two magneto-optical glasses (TG20 and MR3-2) to ultimately create one-way structures based on the Faraday effect. Previously, we fabricated basic waveguides obtaining single-mode guidance at 632 nm (the Faraday effect is strongest near the Tb3+ resonance at 485 nm) in both regimes. kHz regime waveguides were isotropic but had high propagation loss due to associated photodarkening (which could be post-annealed). The propagation loss of the MHz regime waveguides was acceptable due to lower photodarkening, but the waveguides were too narrow to confine light properly because of the very strong focus of the writing beam. To try to combine the lower loss with larger waveguide width, we created overlapping structures using a series of superposed waveguides arranged in rings in MHz regime. The confinement in these multi-ring structures was indeed improved and the structure propagation loss was intermediate between that of one-path waveguides created in kHz and MHz regimes. For most other glasses, MHz FLDW systems operate in a heat-accumulation regime, producing waveguide diameters much larger than the writing laser spot size and superposed waveguides that merge into one by melting. Here, the sub-unit waveguides maintained their individual identity indicating that the heat-accumulation effect was absent.

Original languageEnglish
Title of host publicationIntegrated Optics: Devices, Materials, and Technologies XVIII
EditorsJean Emmanuel Broquin, Gualtiero Nunzi Conti
Place of PublicationWashington, DC
Number of pages7
ISBN (Print)9780819499011
Publication statusPublished - 2014
EventIntegrated Optics: Devices, Materials, and Technologies XVIII - San Francisco, CA, United States
Duration: 3 Feb 20145 Feb 2014

Publication series

NameSPIE - International Society for Optical Engineering Proceedings
PublisherSPIE - International Society for Optical Engineering
ISSN (Print)0277-786X


OtherIntegrated Optics: Devices, Materials, and Technologies XVIII
Country/TerritoryUnited States
CitySan Francisco, CA


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