School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
Nature. 2012 Jan 4;481(7379):62-5. doi: 10.1038/nature10695.
Recent research has uncovered a remarkable ability to manipulate and control electromagnetic fields to produce effects such as perfect imaging and spatial cloaking. To achieve spatial cloaking, the index of refraction is manipulated to flow light from a probe around an object in such a way that a 'hole' in space is created, and the object remains hidden. Alternatively, it may be desirable to cloak the occurrence of an event over a finite time period, and the idea of temporal cloaking has been proposed in which the dispersion of the material is manipulated in time, producing a 'time hole' in the probe beam to hide the occurrence of the event from the observer. This approach is based on accelerating the front part of a probe light beam and slowing down its rear part to create a well controlled temporal gap--inside which an event occurs--such that the probe beam is not modified in any way by the event. The probe beam is then restored to its original form by the reverse manipulation of the dispersion. Here we present an experimental demonstration of temporal cloaking in an optical fibre-based system by applying concepts from the space-time duality between diffraction and dispersive broadening. We characterize the performance of our temporal cloak by detecting the spectral modification of a probe beam due to an optical interaction and show that the amplitude of the event (at the picosecond timescale) is reduced by more than an order of magnitude when the cloak is turned on. These results are a significant step towards the development of full spatio-temporal cloaking.
最近的研究揭示了一种令人惊讶的能力，可以操纵和控制电磁场，以产生诸如完美成像和空间隐形等效果。为了实现空间隐形，折射率被操纵，以使光线从探测器绕过物体流动，从而在空间中产生“孔”，而物体则保持隐藏。或者，可能希望在有限的时间内掩盖事件的发生，因此提出了时间隐形的想法，其中通过时间操纵材料的色散，在探针光束中产生“时间孔”，从而使观察者无法观察到事件的发生。这种方法基于加速探针光束的前端并减慢其后端，以创建一个受控的时间间隙-事件在其中发生-使得探针光束不会被事件以任何方式修改。然后通过色散的反向操纵将探针光束恢复到其原始形式。在这里，我们通过应用衍射和弥散展宽之间的时空对偶性的概念，在基于光纤的系统中展示了时间隐形的实验演示。我们通过检测由于光学相互作用而导致的探针光束的光谱修饰来表征我们的时间隐形的性能，并表明当隐形时，事件的幅度（在皮秒时间尺度上）降低了一个数量级以上。这些结果是朝着完全时空隐形发展迈出的重要一步。
