The Materials Science and Engineering of High Power Lasers
John Ballato, PhD
March 27, 2020
Continued progress in the development of optical fiber-based lasers has led to the present state where further improvements in performance are limited by intrinsic optical nonlinearities. In order to manage such limitations, laser designers have largely adopted the approach of microstructuring the fiber to shift nonlinear thresholds to high optical powers. The nonlinearities are accepted as fixed and performance is enhanced through fiber geometric complexity. This talk treats a different option, which is to mitigate optical nonlinearities at their fundamental origin: the materials with which the light interacts. This work provides a road-map for the development of simple core/clad optical fibers whose enhanced performance – in particular, marked reductions in optical nonlinearities – is achieved materially and not through the more conventional present routes of geometrically complex fiber design. More specifically, the material properties that give rise to Brillouin, Raman, and Rayleigh scattering, transverse mode instabilities (TMI), and n2-mediated nonlinear effects are compiled and results on a wide range of optical fibers are discussed with a focus on trends in performance with glass composition. Further, optical power scaling estimations as well as binary and ternary property diagrams associated with Rayleigh scattering, the Brillouin gain coefficient (BGC) and the thermo-optic coefficient (dn/dT) are developed and employed to graphically represent general trends with composition along with compositional targets for a single intrinsically low nonlinearity, silica-based optical fiber that can achieve the power-scaling goals of future high energy fiber laser applications.
Drop Generation in Electro-Coflows
Josefa Guerrero-Millan, PhD
April 17, 2020
Controlled generation of micron and sub-micron sized drops continues to be of strong interest for the scientific community due to the variety of applications in many different fields. Microfluidics allows the precision manipulation of small volume of fluids and it is used in areas like microanalysis, point-of-care detection and diagnostics, in vitro disease and tissue modeling, and organic synthesis, among others. In our experiments, we use glass-based microfluidics, where 3D flows travel in coaxially aligned glass capillaries producing emulsion drops. In addition to the hydrodynamic stresses, we use electrical stresses to force the drop formation. The presence of charge in the interface of the liquids adds another control parameter in the drop production process. In this talk, we present a qualitative study of jet structure and droplet formation in the different electrohydrodynamic spraying regimes when the hosting media is a flowing dielectric liquid..
Seminar series sponsored by: Augusta University Research Institute, College of Science and Mathematics, Department of Chemistry and Physics