Ultrafast All-Optical Switching of Doped Semiconductor Nanoparticles
by
48/1-112C/D - Redwood C/D
SLAC
The sea of free electrons in a metal results in an electron wave called a surface plasmon which propagates on the metal surface. When confined on a nanometer-scale particle, the surface plasmon forms a localized surface plasmon resonance (LSPR) corresponding to the coherent oscillations of electrons on the particle surface. Due to their strong interaction with light and rapid transmission speeds, surface envisioned as building blocks in light-based computing. Similar to metals, doped semiconductor materials also show surface plasmons. Heavily-doped semiconductor materials, such as In-doped CdO, may be synthesized as colloidal nanoparticles which display infrared LSPRs tunable throughout the infrared spectrum by controlling the impurity doping level. Using infrared optical control pulses, this class of materials can be engineered to achieve exceptionally large sub-picosecond optical non-linearities, including relative changes in transmission and index of refraction of more than 100% at telecommunications wavelengths (1.3 μm or 1.5 μm). The physical origin of these changes is the optically-induced heating followed by cooling of the free electron plasma to high effective temperatures in excess of 5000 K. This class of materials shows promise for terahertz frequency all-optical switching, wavefront engineering, and beam steering in the infrared.