Terahertz plasmonics with semiconductor surfaces and antennas

Semiconductors have a Drude-like behavior at terahertz (THz) frequencies similar to metals at optical frequencies. Narrow band gap semiconductors have a dielectric constant with a negative real component and a relatively small imaginary component. This permittivity is characteristic of noble metals in the visible. Therefore, similar to metals at optical frequencies, semiconductors sustain surface plasmon polaritons (SPPs) or collective oscillations of free charge carriers at the interface with a dielectric. We present here a description of the characteristic lengths of SPPs on semiconductor surfaces. We also consider localized surface plasmon polaritons (LSPPs) in small semiconductor particles or plasmonic antennas. These LSPPs lead to resonances that can be tuned by varying the carrier concentration.