Role of Glass Composition in Waveguide Fabrication with Femtosecond Laser Pulses

Denise Krol, University of California, Davis, DMR-0307002Tightly focused femtosecond (fs) laser pulses can be used for direct writing of waveguides in glass. Prof. Krol and her students have studied the structural changes that are associated with this process. By using confocal fluorescence and Raman microscopy they have been able to show that both localized defects as well as changes in intermediate-range structure occur upon exposure to the fs laser. They have studied how these changes are influenced by glass composition, laser repetition rate and temperature. A comprehensive analysis of all the experimental results indicates that good waveguides are formed below the actual damage threshold of the glass. The rapid quenching model, which correlates the refractive index of the modified material to its cooling rate, explains the effect of composition on waveguide behavior. This work will potentially lead to novel photonic devices with applications in optical data storage, telecommunications, and bio-sensing and –imaging.

Fig. 1. Transverse and b) longitudinal waveguide writing. The black arrows indicate the direction in which the sample is moved.

Fig. 1. Diagrams and spectroscopic signatures of the structural changes associated with fs laser waveguide writing.

Role of Glass Composition in Waveguide Fabrication with Femtosecond Laser Pulses

Denise Krol, University of California, Davis, DMR-0307002

Tightly focused femtosecond (fs) laser pulses can be used to permanently modify the refractive index of glass within the focal region of the laser beam. By moving the sample with respect to the laser focus it is possible to “write” 3-D patterns in the glass. Applications of this -so-called- fs-laser writing technique are in telecommunications, optical data storage, and bio-sensing and –imaging. The ability to use this technique with different glass compositions- tailored for a specific photonics application- is critical to its successful exploitation. The experimental tools that are used for modifying the material can in a different implementation also be used to optically and spectroscopically characterize a material with high spatial resolution.

Role of Glass Composition in Waveguide Fabrication with Femtosecond Laser Pulses

Denise Krol, University of California, Davis, DMR-0307002

Three graduate students and three undergraduate students have contributed to this project. The undergraduate students are in the Optical Science and Engineering Program at UC Davis and this project gives them a unique opportunity to get hands-on experience with state-of-the-art optical techniques, which serve as an important skill-base for any career involving optical materials science and technology. This project has resulted in 7 contributed (presented by one of the graduate students) and 8 invited presentations at major international conferences. One of the presentations has been disseminated as a learning resource for the glass community by the NSF-IMI “New Functionalities in Glass” , where the PI serves as a board member, in the form of a video module.

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Graduate students in the lab