Ultrabroadband perfect imaging in terahertz wire media using single-cycle pulses
Ultrabroadband perfect imaging in terahertz wire media using single-cycle pulses
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DOI：
10.1364/optica.3.000458
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发表时间：
2016-05-20
期刊：
影响因子：
10.4
通讯作者：
Fischer, Bernd M.
中科院分区：
文献类型：
--
作者：
Kaltenecker, Korbinian J.;Tuniz, Alessandro;Fischer, Bernd M.
由线介质超材料形成的平板能够在几个波长上传输倏逝波，并且能够在如此长的距离上对具有深亚波长特征的场图案进行完美成像。到目前为止，完美的成像已被限制到由法布里-珀罗（FP）共振条件定义的窄频率窗口。远离这样的共振，板内的背反射导致由线介质支持的表面波的激发。这导致图像失真，从而严重限制了宽带亚波长成像的有线介质的使用。在这里，我们提出并证明，这种限制可以克服使用超短电磁脉冲作为场源，允许分离的初始脉冲从随后的背反射，这是不能实现使用连续波源。使用太赫兹（THz）近场显微镜的基础上的时域方法，我们证明了超宽带传输的失真无图像在整个频带的源（0.1-1.75太赫兹）。这样的性能要求板足够长;这种方法的限制也通过成像具有高Q因子的谐振模式通过短板来证明。我们的研究结果为在基于短电磁脉冲的宽带成像应用中实现有线介质铺平了道路，例如太赫兹脉冲成像或使用超短激光脉冲的光学成像。(C)2016美国光学学会
Slabs formed by wire medium metamaterials are capable of transmitting evanescent waves over several wavelengths, and enable perfect imaging of field patterns with deeply subwavelength features over such long distances. To date, perfect imaging has been limited to narrow frequency windows defined by the Fabry-Perot (FP) resonance condition. Away from such resonances, backreflections within the slab result in the excitation of surface waves supported by the wire medium. This leads to image distortions, thus severely limiting the use of wire media for broadband subwavelength imaging. Here, we propose and demonstrate that this limitation can be overcome by using ultrashort electromagnetic pulses as the field source, allowing separation of the initial pulse from subsequent backreflections, which cannot be achieved using continuous-wave sources. Using a terahertz (THz) near-field microscope based on a time-domain approach, we demonstrate ultrabroadband transmission of distortion-free images over the entire frequency band of the source (0.1-1.75 THz). Such performance requires the slabs to be sufficiently long; the limits of this approach are also demonstrated by imaging a resonant mode with high Q-factor through a short slab. Our results pave the way for the implementation of wire media in broadband imaging applications based on short electromagnetic pulses, such as THz pulse imaging or optical imaging with ultrashort laser pulses. (C) 2016 Optical Society of America