Ultrafast lasers with pulses shorter than a trillionth of a second can be used to create micron-sized structures inside a piece of glass. This fabrication method provides a platform for the fabrication of photonic devices and circuits with applications in optical communications, bio-imaging and -sensing and nanotechnology. In order to exploit the full potential of this ultrafast laser 'writing' technique it is important to design materials that are optimized both in terms of device properties and laser processing behavior. Towards this goal this project aims to develop such materials as well as a detailed understanding of how the laser changes the materials structure on a microscopic scale. The research is a collaboration between UC Davis and Missouri S&T and provides training for graduate, undergraduate and pre-college students in state-of-the-art materials science and optical techniques, research opportunities for undergraduates and outreach activities at the pre-college level.
TECHNICAL DETAILS: Femtosecond (fs)-laser writing of optical waveguides inside glass substrates is a promising technique for fabricating integrated photonic devices. The quality of the device is determined by the response of the glass to fs laser processing conditions as well as glass composition. Phosphate glasses, which are of interest as host materials for active devices since they allow incorporation of high concentrations of rare earth ions, typically produce negative refractive index changes in the laser-exposed regions, leading to poor optical performance. However, certain compositions exhibit positive refractive index changes that are desirable for device fabrication. The overall objective of the project is to develop a fundamental understanding of the materials parameters that govern the response of phosphate glass to femtosecond laser irradiation. Experiments are conducted to determine the relationships between glass structure and response to fs-laser processing and to characterize fs-laser induced changes in glass structure using fluorescence, Raman, micro-NMR and ESR techniques, among others. The experimental results are used to develop a model that describes the fs-laser response in terms of relevant glass structural parameters and ultimately design new glass compositions. This project is a collaboration between groups with expertise in optical materials and laser physics (UC-Davis) and glass chemistry (Missouri S&T) and provides training for graduate students in state-of-the-art materials science and optical techniques, research opportunities for undergraduates and outreach activities at the pre-college level.