Experimental study of a terahertz time-domain spectrometer based on photoconductive antenna

We construct a terahertz time-domain spectrometer (THz-TDS) system based on photoconductive antenna (PCA). A 800 nm Ti sapphire femtosecond laser with 80 MHz repetition rate provides the pump and probe laser pulse, which has a 45 fs pulse width (as short as 15 fs is available) and as much as 400 mW power. Two commercial PCAs with 34 um and 6 um gap size are used as the emitter and receiver, respectively. We characterize this system by measuring its absolute radiated THz power, spectral bandwidth, signal-to-noise ratio (SNR), dynamic range and beam profile at the focal plane. We further analyze the noise sources of the THz-TDS system and specifically discuss the possibility to improve the DR and SNR. In addition, using this system, we study the response of the PCA to various parameters, such as laser power, biased voltage, beam spot's location and laser's polarization.