Schwartz O, Axelrod J J, Tuthill D R, Haslinger P, Ophus C, Glaeser R M, Müller H
Opt Express. 2017 Jun 26;25(13):14453-14462. doi: 10.1364/OE.25.014453.
Manipulating free-space electron wave functions with laser fields can bring about new electron-optical elements for transmission electron microscopy (TEM). In particular, a Zernike phase plate would enable high-contrast TEM imaging of soft matter, leading to new opportunities in structural biology and materials science. A Zernike phase plate can be implemented using a tight, intense continuous laser focus that shifts the phase of the electron wave by the ponderomotive potential. Here, we use a near-concentric cavity to focus 7.5 kW of continuous-wave circulating laser power at 1064 nm into a 7 µm mode waist, achieving a record continuous laser intensity of 40 GW/cm. Such parameters are sufficient to impart a phase shift of 1 rad to a 10 keV electron beam, or 0.16 rad to a 300 keV beam. Our numerical simulations confirm that the standing-wave phase shift profile imprinted on the electron wave by the intra-cavity field can serve as a nearly ideal Zernike phase plate.
利用激光场操纵自由空间电子波函数可带来用于透射电子显微镜（TEM）的新型电子光学元件。特别是，泽尼克相板将使软物质的高对比度TEM成像成为可能，为结构生物学和材料科学带来新机遇。泽尼克相板可通过紧密、高强度的连续激光聚焦来实现，该聚焦通过有质动力势使电子波的相位发生偏移。在此，我们使用近同心腔将1064 nm波长的7.5 kW连续波循环激光功率聚焦到7 µm的模腰中，实现了40 GW/cm的创纪录连续激光强度。这样的参数足以使10 keV电子束产生1 rad的相移，或使300 keV电子束产生0.16 rad的相移。我们的数值模拟证实，腔内场印刻在电子波上的驻波相移轮廓可作为近乎理想的泽尼克相板。
