OSC Colloquium: Dr. David Tsu

    Thursday, October 3, 2019 - 3:30pm - 5:00pm
    Meinel 307

    1630 E. University Blvd.

    3rd Floor Lobby area


    Open to campus and public.


    Speaker: Dr. David Tsu

    Topic:The Study of Light Scattering from its beginnings in Astronomy, to understanding Haze in polymers, to helping Cosmology?

    Host: Masud Mansuripur 

    Visit our website for future lecture dates and speaker information: http://www.optics.arizona.edu/news-events/events/colloquium For a list of our archived lectures: http://www.optics.arizona.edu/news-events/events/colloquium/archive


    Before discussing scattering, I will briefly start off talking about the meaning of Spectroscopy and what a Spectroscopist does. For some reason, the subject of light scattering in not taught in any meaningful way, especially at the Undergraduate level. But without such research, our knowledge of our Universe would be entirely inadequate. Lord Rayleigh started it all with his accurate description of Blue Sky. Then Astronomers, like H.C. van de Hulst, used scattering theory to understand the Interstellar Medium. My interest in scattering started with trying to understand if this technique can be used to understand the disorder in a-Si:H used in thin film solar cells. Now, my interest in scattering has turned to studying the reasons that polymers have higher levels of Haze compared to glass. The direction of advanced new technologies is turning ever more away from using glass displays, and toward polymer displays. In Mackinac, we are developing high energy efficient coatings on polymers to greatly reduce the energy flow out windows and at low cost. Needless to say, an important part of our research is to reduce the Haze in polymers. To this end, I’ve developed a Parametric Power Law (PPL) analysis tool to help quantify the size and number density of the scattering centers from simple spectroscopic measurements using an integrating sphere to gather the scattered light. Along the way, the shortcomings of scattering theory hit hard. While Rayleigh scattering (RS) is for small molecules/atoms, then there is a natural extension to Rayleigh-Gans (R-G) scattering for large molecules and nano-sized particles. But for micron sized particles, we jump to Mie scattering (MS) theory. The transition from R-G to MS is a no-man’s land where no theory applies. In both RS and R-G, the concept of refractive index does not apply, but then it is suddenly used in MS, where my use of PPL clearly shows this no-man’s land. In order to “fix” this problem, I have applied the simple reasoning that these theories must smoothly join, and so I’ve applied a logarithmic interpolation. Clearly though, this does not solve the problem, as significant theoretical work needs to be done to develop a true Unified Scattering Theory (UST). Lastly, I’ve been thinking about the old problem of why the night sky is dark. It is true that Olber’s paradox has largely been solved by the Big Bang theory. But this discussion does not involve the effects of scattering. If we believe in Quantum Mechanics, then the Vacuum state cannot truly be empty, and this means that there must be a background scattering halo of visible light. It must also mean that there is a reddening of light that is not related to cosmic expansion. There just might be some evidence for this after all!

    Speaker Bio(s): 

    Dr. Tsu received his Bachelor’s degree from Univ. of Washington in Seattle, and his Ph.D. in Physics from North Carolina State Univ., in Raleigh NC. After a Post Doc at Northwestern Univ., he joined the Research division at Energy Conversion Devices in Troy Michigan. To say that ECD was an interesting place is no joke. ECD’s founder and leader, Stan Ovshinsky was interested in many things, including high temperature super conductors. ECD was by far the world’s leader in amorphous silicon technologies, the inventor of Ni:Metal hydride rechargeable battery technology, as well as the inventor of optical rewritable disc technology. And through it all, I have worked on all these t echnologies as ECD’s Chief Spectrocopist, where I have touched about 1/4 of the elements in the Periodic Table. It was during our work in developing the next generation of optical recording media that my path crossed with Prof. Masud Mansuripur. Then in 2007, new management at ECD kicked out Ovshinsky, and got the bright idea that they wanted ECD to be profitable. So their first action was to abolish the whole Research Division. So out on the street, I formed Ming Scientific, an energy consulting company, to understand how to improve the energy efficiency of buildings and factories. Due to certain advanced technology that Ming developed, the US Postal Service hired Ming, as did the Cobo Center (home of Detroits North American Auto Show) to lead the analysis of Cobo’s exterior “envelope” for their $280 Million renovation project. In 2009, Dr. Tsu met John Slagter, founder of Mackinac Tech. Co., because John was advised that he needed a Spectroscopist on his team. We collaborated on various projects and proposals, then in 2013, John decided to hire me full time as his Chief Scientist. Since then, we have worked on successful Phase-I and -II project from the US DoT, was awarded a two year ARPA-e program to develop our advanced window system, and have enjoyed support by the US Army Corp of Engineers. In short, Dr. Tsu’s career started in the very early days of the Renewable Energy sector (when this was not cool), to the study and analysis of Energy Efficiency of buildings, and now to the development of Energy Efficient products for buildings.


    Refreshments 3:30pm

    Lecture @ 3:45pm - 5pm