Theoretical and experimental study of a terahertz time-domain spectrometer based on photoconductive antenna

Summary form only given. 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) and dynamic range. Using this system, we study the response of the PCA as the emitter and receiver to the laser power and/or biased DC voltage, as well as their influences on the SNR and dynamic range of the TDS system. In addition, we present a 3D full-wave finite-difference time-domain (FDTD) analysis of the PCA-based terahertz source. The modeling consists of two parts. For the first part, the 3D drift-diffusion and continuity equations coupled with Poisson equation are used to simulate the photoconductive carrier generation and transport process. For the second part, the full-wave interaction and propagation analyzed by solving 3D Maxwell´s equation with FDTD method. The coupling between these two parts is implemented by applying the electric field obtained from the Maxwell´s equation to the carrier transport equation. The whole process of THz radiation generated by the laser-pulse-gated PCA can be simulated using this method. We further explore a set of parameter study (such as semiconductor material´s properties, laser power and biased DC voltage) for PCA using the 3D full-wave analysis method, and compare the simulation results with the experiments. It believed that the analysis method can be used as an optimization tool for PCA design and application.