Detection of terahertz radiation from longitudinal optical phonon-plasmon coupling modes in InSb film using an ultrabroadband photoconductive antenna

Terahertz radiation from longitudinal optical (LO) phonon-plasmon coupling modes in InSb films is observed using an ultrafast photoconductive antenna detector. We demonstrate a response frequency of up to 7 THz for a low-temp erature-grown GaAs-based photoconductive antenna gated with 25 fs laser pul ses. It is found that the emission frequencies of the coupling modes are de pendent only on the residual carrier density, not on the excitation carrier density. It is also found that the LO phonon-plasmon oscillations in semic onductors can serve as an efficient THz source. (C) 2000 American Institute of Physics. [S0003-6951(00)04538-1].