Super-High Brightness and High-Spin-Polarization Photocathode
Super-High Brightness and High-Spin-Polarization Photocathode
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DOI：
10.1143/apex.1.045002
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发表时间：
2008-03
影响因子：
2.3
通讯作者：
X. Jin;N. Yamamoto;Y. Nakagawa;A. Mano;T. Kato;M. Tanioku;T. Ujihara;Y. Takeda;S. Okumi;M. Yamamoto;T. Nakanishi;T. Saka;H. Horinaka;T. Kato;T. Yasue;T. Koshikawa
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文献类型：
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作者：
X. Jin;N. Yamamoto;Y. Nakagawa;A. Mano;T. Kato;M. Tanioku;T. Ujihara;Y. Takeda;S. Okumi;M. Yamamoto;T. Nakanishi;T. Saka;H. Horinaka;T. Kato;T. Yasue;T. Koshikawa
采用新开发的透射型光电阴极，实现了超高亮度[(1.3±0.5)×107 A·cm-2·sr-1]的电子束。而且，自旋极化高达90%。我们在GaP衬底上制作了基于GaAs-GaAsP应变超晶格的透射型光电阴极，以大大提高亮度和偏振度。在该系统中，激光束穿过透明的 GaP 基板引入。光束通过短焦距透镜聚焦在超晶格有源层上。激发的电子在小区域内产生并从表面提取。电子产生面积的缩小提高了亮度。此外，在GaP衬底和GaAsP缓冲层之间插入GaAs层以控制GaAsP缓冲层中的应变弛豫过程。这种应变控制设计是透射型光电阴极实现高偏振（90%）的关键。
Using a newly developed transmission-type photocathode, an electron beam of super-high brightness [(1.3±0.5)×107 A·cm-2·sr-1] was achieved. Moreover, the spin-polarization was as high as 90%. We fabricated a transmission-type photocathode based on a GaAs–GaAsP strained superlattice on a GaP substrate in order to enhance the brightness and polarization greatly. In this system, a laser beam is introduced through the transparent GaP substrate. The beam is focused on the superlattice active layer with a short focal length lens. Excited electrons are generated in a small area and extracted from the surface. The shrinkage of the electron generation area improved the brightness. In addition, a GaAs layer was inserted between the GaP substrate and the GaAsP buffer layer to control the strain relaxation process in the GaAsP buffer layer. This design for strain control was key in achieving high polarization (90%) in the transmission-type photocathode.