terahertz spectroscopy based on the coherent Cherenkov radiation emitted from femto-second electron bunch

研究了一种新的太赫兹光谱学方法。该方法基于两种现象：超短电子束发出的相干辐射和电子通过介电材料表面附近引起的切伦科夫辐射。当电子速度超过介电体内部辐射的相速度时，产生相干切伦科夫辐射。100飞秒光注入器的研制表明，饱和电流密度远高于长脉冲电子枪，并且在饱和状态下电子束长度明显延长。在辐射研究中，观测到了切伦科夫辐射产生的阈值加速电压。实测阈值与理论预测吻合较好。我们得出结论，相干切伦科夫辐射光谱的原理可以被证明。

A novel terahertz spectroscopy method has been investigated. The method is based on two phenomena: the coherent radiation emitted from the ultra-short electron bunch and Cherenkov radiation induced by electron passing vicinity of the surface of dielectric materials. Coherent Cherenkov radiation is produced when the electron velocity exceeds the phase velocity of the radiation inside the dielectrics.Development of a 100 femto-second photoinjector revealed that the saturation current density was much higher than that of the long-pulsed electron gun, and the remarkable elongation of the electron bunch length under the saturation. In the study of the radiation, the threshold acceleration voltage for the generation of the Cherenkov radiation was observed. Measured threshold was agreed well with the theoretical prediction. We conclude that the principle of the Coherent Cherenkov radiation spectroscopy could be demonstrated.