Speaker: Joshua caldwell, Vanderbilt University
Title: Strong Coupling in Polaritonic Media: Towards On-Chip Infrared Nanophotonics
Abstract: The field of nanophotonics is based on the ability to confine light to sub-diffractional dimensions. In the infrared, this requires compression of the wavelength to length scales well below that of the free-space values. While traditional dielectric materials do not exhibit indices of refraction high enough in non-dispersive media to realize such compression, the implementation of polaritons, quasi-particles comprised of oscillating charges and photons, enable such opportunities. Two predominant forms of polaritons, the plasmon and phonon polariton, which are derived from light coupled with free carriers or polar optic phonons, respectively, are broadly applied in the mid- to long-wave infrared. However, the short scattering lifetimes of free-carriers results in high losses and broad linewidths for the former, while the fast dispersion and narrow band of operation for the latter result in significant limitations for both forms. Here we will discuss the opportunity to implement polaritonic strong coupling between different media in an effort to dictate the polaritonic dispersion relation, and thus, the propagation and resonant properties of these materials. Within the talk results highlighting ultra-strong coupling in both forms of polaritons will be presented in the context of infrared emitters, as a means to control planar propagation using hyperbolic polaritons and in an effort to dictate the IR dielectric function using superlattice designs.
Bio: Dr. Caldwell obtained his B.A. in Chemistry in 2000 from Virginia Tech with a minor in History. Following this, he attended the University of Florida where he received his Ph.D. in Physical Chemistry in 2004. He accepted an American Society of Engineering Education Postdoctoral Fellowship to the US Naval Research Laboratory in 2005, where he was hired on as a staff scientist in 2007. He was promoted to a supervisory role in 2012. In 2013-2014 Dr. Caldwell worked with Prof. Kostya Novoselov at the University of Manchester during a Sabbatical, where they worked on identifying two-dimensional materials for infrared nanophotonics, identifying hexagonal boron nitride as a natural hyperbolic material. During his time at NRL he was the recipient of three highly competitive Nanoscience Institute Grants and several awards for his published works. In 2017 he accepted a tenured Associate Professorship in the Mechanical Engineering Department at Vanderbilt University.
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