Minerbi Eviatar, Keren-Zur Shay, Ellenbogen Tal
Nano Lett. 2019 Sep 11;19(9):6072-6077. doi: 10.1021/acs.nanolett.9b01970. Epub 2019 Aug 1.
We introduce a nanoengineered nonlinear metasurface based optical element that acts as an emitting Fresnel zone plate of terahertz (THz) waves. We show that the nonlinear zone plate generates broadband THz radiation and focuses each generated frequency on a different focal point along the optical axis. Therefore, a narrow beam waist and spectral selectivity of both the bandwidth and central frequency are achieved. Furthermore, we measure and analyze the temporal structure of the focused THz electric field and show that it comprises of few cycles with an axially varying carrier frequency in agreement with the calculated dispersion of the zone plate. This demonstration of controlled emission and focusing of THz waves opens the door for the development of a wide variety of additional holographic metasurface-based THz emitters and can lead to the development of efficient, active, integrated, and ultracompact optical devices for the THz spectral region.
我们介绍了一种基于纳米工程非线性超表面的光学元件，它可作为太赫兹（THz）波的发射菲涅耳波带片。我们表明，非线性波带片可产生宽带太赫兹辐射，并将每个产生的频率聚焦在光轴上的不同焦点处。因此，实现了窄束腰以及带宽和中心频率的光谱选择性。此外，我们测量并分析了聚焦太赫兹电场的时间结构，结果表明它由几个周期组成，其载波频率沿轴向变化，这与波带片计算出的色散一致。太赫兹波的这种可控发射和聚焦演示为开发各种基于全息超表面的额外太赫兹发射器打开了大门，并可能导致开发用于太赫兹光谱区域的高效、有源、集成和超紧凑型光学器件。
