Generation and detection of ultrabroadband terahertz (THz) radiation were well exploited by using electro-optic crystals as the emitter and detector. A recent report showed a spectral distribution of THz radiation extending up to 100 THz, using thin electro-optic (EO) crystals as the emitter (GaSe) and detector (ZnTe). On the other hand, the spectral bandwidth of THz radiation obtained with photoconductive (PC) antennas, the major alternative method to the EO technique for generation and detection of THz radiation, was believed to be limited less than 7 THz due to the slow response of real carriers or the finite RC time-constant of the photoconductive antennas. In recent studies we demonstrated that PC antennas made with low-temperature-grown (LTG) GaAs are also able to detect electromagnetic radiation at frequencies well beyond 10 THz when they are triggered with short enough laser pulses (< 20 fs). On the other hand, generation of ultrabroadband THz radiation beyond 10 THz with PC antennas was not confirmed so far. In this paper, we report generation of an ultrabroadband THz radiation, whose spectral distribution exceeded 10 THz, with a PC emitter excited with ultrashort laser pulses (～20 fs).
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