Terahertz radiation from LO phonon-plasmon coupling modes in InSb film

In this work we present broadband coherent measurements of THz radiation from an InSb film using a PC antenna detector. Ultrashort laser pulses and tight focusing of the gate laser beam on the electrode gap of the antenna detector enabled us to extend the response bandwidth of the detector to 7 THz. By using this ultrabroadband PC antenna detector, we observed the THz radiation from LO phonon-plasmon oscillations in InSb film for the first time. It was found that the radiation power was comparable to that originating from the photo Dember field on the InSb film surface. This suggests that the LO phonon-plasmon oscillations can serve as an efficient source for THz radiation.