Measuring the field of visible light with high spatial resolution has been challenging, as many established methods only detect a focus-averaged signal. Here, we introduce a near-field method for optical field sampling that overcomes that limitation by employing the localization of the enhanced near-field of a nanometric needle tip. A probe field perturbs the photoemission from the tip, which is induced by a pump pulse, generating a field-dependent current modulation that can easily be captured with our electronic detection scheme. The approach provides reliable characterization of near-petahertz fields. We show that not only the spiral wavefront of visible femtosecond light pulses carrying orbital angular momentum (OAM) can be resolved but also the field evolution with time in the focal plane. Additionally, our method is polarization sensitive, which makes it applicable to vectorial field reconstruction.

中文翻译：

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近拍赫兹涡旋场的时空采样

以高空间分辨率测量可见光场一直具有挑战性，因为许多已建立的方法仅检测焦点平均信号。在这里，我们介绍了一种用于光场采样的近场方法，该方法通过采用纳米针尖的增强近场的定位来克服该限制。探针场扰乱了尖端的光发射，这是由泵脉冲引起的，产生与场相关的电流调制，可以通过我们的电子检测方案轻松捕获。该方法提供了近拍赫兹场的可靠表征。我们表明，不仅可以解决携带轨道角动量（OAM）的可见飞秒光脉冲的螺旋波前，而且还可以解决焦平面中随时间的场演变。此外，我们的方法对偏振敏感，