Surface Phonon Polaritons for Low Loss Infrared to THZ Nanophotonics

Seminar | April 12 | 4-5 p.m. | 348 Hearst Memorial Mining Building

 Dr. Joe Tischler, Naval Research Laboratory

 Materials Science and Engineering (MSE)

Progress in plasmonic research has demonstrated its capability for enhancing many technologies including photodetectors, photovoltaics, and molecular spectroscopy. However, in order to maximize functionality, alternative materials to plasmonic metals that exhibit high optical losses must be explored.
In our studies we have demonstrated that plasmonic like effects can be achieved through phonon mediated collective charge oscillations, called surface phonon polaritons (SPhPs) in polar dielectric materials such as SiC and InP. Recently we showed that localized SPhP nanopillar resonators support extreme sub-diffraction (λres/200) compression of the free space wavelength, with very low optical
losses, resulting in quality factors up to an order of magnitude higher than the best plasmonic devices. Furthermore, the sharp plasmonic-like resonances can be actively tuned and/or turned off through optical pumping of electron/holes carriers.
The use of polar dielectrics to achieve plasmonic like effects is only in the beginning stages of exploration. In particular SPhP in polar anisotropic 2D crystals such as hBN can be exploited as natural
hyperbolic materials (NHM). We have exploited the NHM response of hBN within periodic arrays of conical nanoresonators to demonstrate ‘hyperbolic polaritons’, deeply sub-diffractional guided waves
that propagate through the volume rather than on the surface of a hyperbolic material. We have identified that the polaritons are manifested as a four series of resonances in two distinct spectral bands that have mutually exclusive dependencies upon incident light polarization, modal order, and aspect ratio. These findings can be extended to produce hyperbolic materials exploiting surface phonon
polaritons in layered III-V semiconductors and other 2D materials to extend the optical range and physics. Novel devices and future directions will also be discussed.

 daisyh@berkeley.edu, 510-642-3801