通过对半导体太赫兹发射极在有和没有外加电场和磁场作用下发射光谱的测量,说明了外加电场和磁场对太赫兹电磁辐射的产生具有增强作用。采用反射式发射极在飞秒激光作用下辐射太赫兹脉冲的装置,同时利用电光取样方法探测太赫兹电场,得到了这些发射极的时域发射光谱,并通过快速傅里叶变换(FFT)得到了相应的频域光谱。实验表明,太赫兹时域发射光谱和频谱在外加电场、磁场作用下都有增强,但是所发射的频率成分和带宽都没有改变。借助于经典电磁理论的定性分析,认为太赫兹发射光谱在外加电场、磁场作用下的增强起源于半导体中载流子的加速运动受外加电场和磁场的影响。

In this paper, the effects of the applied electrical and magnetic field on the generation of optically induced terahertz (THz) electromagnetic radiation are reported by measuring the signal from the semiconductor emitter. The biased electrical field and magnetic field can enhance optically induced THz electromagnetic radiation. The emission spectra of time domain of semiconductors biased by applied electrical and magnetic field are obtained by the use of the reflection-type emitter irradiated by the femtosecond laser and the electro-optic sampling. The corresponding frequency domain spectra are obtained by fast Fourier transform (FFT). The results show that THz emission spectra are enhanced by the applied electrical and magnetic field, while their frequency components and bandwidths are not changed. By the classical electromagnetic theory, the effect of applied electrical and magnetic field on THz emission can be attributed to the acceleration motion of carriers in semiconductors.