Study on a free electron laser in a THz region using a modulation beam emitted from a micro-field emitter

1.我们观察到史密斯-珀塞尔辐射试图通过从微场发射器发射的直流电子束在铝栅上。束流为200nA，加速电压为25~30KV，栅距为416 nm。观测到的辐射为350 nm附近的四次谐波、400 nm附近的三次谐波、600 nm附近的二次谐波和1300 nm附近的基波。观察到的Smith-Purcell辐射的波长符合Smith-Purcell理论。2.要实现自由电子激光，需要一个高频电子脉冲光束。为了产生高频脉冲光束，我们研制了一种采用湿法刻蚀的p型砷化镓发射体的制作工艺。我们对GaAsa发射体进行了(NH4)2Sx表面处理。结果表明，由于处理消除了表面氧化物，改善了表面粗糙度，防止了表面氧化，使得p型发射极的发射电流达到了明显的饱和。3.我们还开发了一种用于产生高频呕吐光束的GaAs光阴极的制作工艺。我们用YO-YO方法在砷化镓表面形成负电子亲和势。结果，我们成功地制作出量子效率为2%的GaAs光阴极。

1.We observed Smith-Purcell radiation try passing a dc-electron beam emitted from a micro field emitter on an Al grating. The beam current, and acceleration voltage were 200nA and 25-30kV, respectively The pitch of the grating was 416nm. The observed radiations were 4th harmonic one in the ultraviolet region around 350nm, 3rd harmonic one around 400nm, 2nd harmonic one around 600nm, and fundamental one around 1300nm. The wavelength of the observed Smith-Purcell radiation agrees with the smith-Purcell theory.2.To realize a free electron laser, a high frequency electron pulsed beam is necessary. We have developed a fabrication process of a p-type GaAs emitter using a wet etching for the generation of the high frequency pulsed beam. We performed the (NH4)2Sx surface treatment on GaAs a emitter. As the result, we observed a clear saturation of the emission current for the p-type GaAs emitter, because the treatment eliminated the surface oxide, improved the surface roughness, and prevent the oxidation of the surface.3.We also develop a fabrication process of a GaAs photocathode for the generation of the high frequency puked beam. We employed a Yo-Yo method for making a negative electron affinity of the GaAs surface. As the result, we have succeeded in fabricating a GaAs photocathode with a quantum efficiency of 2%.