Time- and Frequency-Resolved Electrodynamics of Germanium Nanoantennas for Mid-Infrared Plasmonics

We investigate the mid-infrared response of heavily doped germanium films and periodic arrays of nanoantennas by both continuous wave transmission/reflection spectroscopy and ultrafast pump-probe spectroscopy. We compare the data to finite-element modeling electromagnetic simulations of the subwavelength nanostructures. The plasma frequency of the doped or optically activated semiconductor extends in the 1000-2000 cm-1 range thus enabling access to molecular fingerprints