Figuring Thin Optical Components Using Ultrashort Pulsed Laser Stress

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This grant will support research that will contribute new knowledge related to manufacturing lightweight optical components like lenses and mirrors. Laser stress bending is a manufacturing process involving focusing a laser into glass mirrors or other optical components under conditions which lead to the material permanently bending into a particular shape. Lightweight optical components are critical for national defense as in space communication and remote imaging, and consumer devices as in virtual reality headsets or smartphones. Laser stress bending has the potential to create accurate lightweight optical components at far lower cost than is possible today because the process speed can be higher than existing optical manufacturing techniques. The laser stress figuring process it not yet fully understood, and this award supports fundamental research to provide knowledge needed to help advance laser stress bending to an industrial process that can benefit the U.S. economy, society, and national defense. This multi-disciplinary research combines manufacturing, materials science, optics, and mechanical engineering and will enhance engineering education. This research will provide research training activities that broaden participation of underrepresented groups including first-generation students.Laser stress figuring of high-aspect ratio optical substrates can provide similar equivalent material removal rate as conventional polishing but applied after coating or mounting and with potentially higher accuracy. Ultrashort pulsed laser stress figuring depends on creating controllable, repeatable, and stable stress at specific locations. Such laser-generated stress has been shown to be driven by at least four mechanisms depending on process parameters: densification, nanograting formation, explosive void formation, and quenching. This research fills the knowledge gap of between the generated stress and the optical pulses within these regimes, addressing the stability and repeatability of the stress, and the utility of this stress in shaping optical components. The research team will conduct experiments using spatially shaped ultrashort laser pulses and in-situ curvature metrology to measure multi-directional stress, model the connection between microscopic stress and macroscopic deformation, measure strength and stability of shaped glass substrates, and quantify manufacturing-relevant quantities such as equivalent material removal rate, accuracy, and convergence rate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.