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arXiv 1604.05929physics.optics
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具有亚衍射斑点的超振荡电子波函数

Super-oscillating Electron Wave Functions with Sub-diffraction Spots

Roei Remez, Yuval Tsur, Peng-Han Lu, Amir H. Tavabi, Rafal E. Dunin-Borkowski, Ady Arie

摘要:

大约一个半世纪前,Ernst Abbe [1]和不久之后的Rayleigh勋爵[2]表明,当光学透镜被平面波照射时,获得半径为0.61*lambda/sin(alpha)的衍射极限光斑,其中lambda是波长,alpha是光束会聚锥的半角。然而,当透镜被适当结构化的光束照射时,可以在焦平面处获得具有小得多的特征的光斑。鉴于这个概念是已知的光束,在这里,我们展示如何实现它的自由电子的双粒子波函数。我们实验证明了半径为106 pm的电子中心点,这是比所使用的实验装置的衍射极限小两倍以上。此外,我们还证明了这个中心光斑可以通过添加轨道角动量来构造,由此产生的超振荡涡旋光束相对于常规涡旋光束具有更小的暗核。这种具有任意小特征和定制结构的热点的新电子束家族可以用于研究亚原子分辨率的电子-物质相互作用。

英文摘要:

Almost one and a half centuries ago, Ernst Abbe [1] and shortly after Lord Rayleigh [2] showed that when an optical lens is illuminated by a plane wave, a diffraction-limited spot with a radius 0.61*lambda/sin(alpha) is obtained, where lambda is the wavelength and alpha is the semi-angle of the beam's convergence cone. However, spots with much smaller features can be obtained at the focal plane when the lens is illuminated by an appropriately structured beam. Whereas this concept is known for light beam, here, we show how to realize it for massive-particle wave function of a free electron. We experimentally demonstrate an electron central spot of radius 106 pm, which is more than two times smaller than the diffraction limit of the experimental setup used. In addition, we demonstrate that this central spot can be structured by adding orbital angular momentum to it. The resulting super-oscillating vortex beam has a smaller dark core with respect to the regular vortex beam. This new family of electron beams having hot-spots with arbitrarily small features and tailored structure can be useful for studying electron-matter interactions with sub-atomic resolution.

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