ECE Seminar: Aaswath P. Raman Seminar Aaswath P. Raman Stanford University Ginzton Laboratory Light refreshments will be available at 10:45 pm outside of PHO 339 Faculty Host: Siddharth Ramachandran Broadband Nanophotonic Devices: Controlling Thermal Radiation and Light Absorption for Energy, Information and Sensing Applications   Abstract: Meeting increasing global demand for energy, especially in the developing world, while reducing carbon emissions remains one of the grand challenges of this century. Nanophotonic devices, by their small length scales, allow researchers to manipulate light and heat in unprecedented ways, enabling new possibilities for energy efficiency and generation to meet this challenge. In this talk, Raman will show how controlling the electromagnetic fields associated with thermal radiation and solar absorption using nanophotonic devices can fundamentally enable new technological capabilities for clean energy, by allowing us to better use both sunlight and an unexploited renewable thermodynamic resource: the cold of space. Moreover, Raman will show how researchers can better characterize the fundamental behavior of nanophotonic devices over a broad range of wavelengths to improve their capabilities in information and sensing applications.   Air conditioning is a significant end-use of energy globally and a major driver of peak electricity demand. At night, electricity-free cooling below ambient air temperature has been demonstrated using a technique known as radiative cooling or night-sky cooling, where one uses a device exposed to the sky to radiatively emit heat to outer space through a transparency window in the atmosphere between 8-13 µm. Raman will present results of the first experimental demonstration of daytime radiative cooling, where a sky-facing nanophotonic surface passively achieved a temperature of 5-10°C below the ambient air temperature under direct sunlight. Raman will also discuss related work on using thermal nanophotonic approaches to passively maintain solar cells at lower temperatures, while maintaining their solar absorption, thereby improving their efficiency.   Raman will next present a nanophotonic light trapping theory that describes broadband light absorption enhancement in nanoscale solar cells. Conventional light trapping increases the path length of incident solar light in the active material, which improves efficiency and cost-effectiveness. He will show that, at the nanoscale, it is possible to exceed conventional limits on light trapping for all absorption regimes, and explain the mechanisms for this enhancement using a rigorous theory. More generally, understanding the broadband behavior of nanophotonic devices is important for not only energy, but also information and sensing applications. Thus, Raman will finally discuss a plasmonic and metamaterial band theory that allow us to rigorously model an important class of nanophotonic devices made of metallic or dispersive elements, over a broad range of wavelengths. This band theory further enables the development of a perturbation theory that can predict the performance of this class of devices in sensing and modulation device scenarios.     Speaker Bio: Aaswath Raman is an Engineering Research Associate with the Ginzton Laboratory at Stanford University. He received his Ph.D. in Applied Physics from Stanford University in 2013, and his A.B. in Physics & Astronomy and M.S. in Computer Science from Harvard University in 2006. His research interests include nanophotonics, thermal science, solid-state devices and renewable energy systems. In 2013, he was the recipient of the Stanford Postdoctoral Research Award, and in 2011, the SPIE Green Photonics Award for his work on nanophotonic light trapping for solar cells, and the Sir James Lougheed Award of Distinction from the Government of Alberta, Canada. In 2015, he received MIT Technology Review’s Innovator Under 35 (TR35) Award for being an Energy Pioneer.