Function analysis of loop inductance in photo-conductive terahertz source

Abstract

Photo-conductive terahertz source (PCA) has been widely used in the terahertz time-domain spectral system (THz-TDS). In the THz-TDS system, the biased PCA is triggered by a femtosecond laser to radiate terahertz waves to free space due to the accelerated motion of photogenerated carriers under the bias electric field, and a pulse current is formed in the PCA bias loop. Generally, the circuit that loads bias voltage to PCA has different circuit designs, so there is inevitably a specific inductance in the base circuit of PCA mounting. The electromagnetic inertia caused by this will significantly affect the pulse width of the current in the circuit. The pulse width of the current pulse will be widened with the increase of the circuit inductance. Therefore, whether the inductance of The PCA circuit will affect the character of the THz wave radiated from PCA to free space is a problem faced by the circuit design based on PCA. In this paper, inductance elements with different inductance values are added to the PCA circuit, and the time domain waveform and spectrum of THz wave radiated by PCA are tested experimentally. The results show that the inductance value in the PCA circuit has no noticeable effect on the THz wave released by PCA, thus providing an experimental basis for designing the THz PCA substrate circuit applied on different occasions.