光电导太赫兹源回路电感对其辐射特性的影响

Influence of inductance of photo-conductive terahertz source circuit on its radiation characteristics

光电导太赫兹源(Photo-Conductive Antenna,PCA)已广泛用于太赫兹时域光谱系统(THz-TDS)。在THz-TDS系统中,处于偏置状态的PCA被飞秒激光触发因光生载流子,在偏置电场下的加速运动而向自由空间辐射太赫兹波,同时在PCA偏置回路中形成脉冲电流。通常给PCA加载偏置电压的回路有不同结构的电路设计,导致PCA装架的基板回路不可避免地存在一定电感,由此引起的电磁惯性会显著影响回路中脉冲电流的脉宽,电流脉冲的脉宽会随回路电感的增大而展宽。那么PCA回路电感是否会影响PCA向自由空间辐射THz波的特性,这是设计PCA基板电路面临的问题所在。本文尝试在PCA回路中加入不同电感值的电感元件,通过实验测试了PCA辐射THz波的时域波形和频谱,结果表明,PCA回路电感的数值对PCA辐射THz波没有明显影响,从而对不同场合应用的PCA基板结构和电路设计提供了实验基础。

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 t designing the THz PCA substrate circuit applied to different occasions.