McKinney Robert W, Monnai Yasuaki, Mendis Rajind, Mittleman Daniel
Opt Express. 2015 Oct 19;23(21):27947-52. doi: 10.1364/OE.23.027947.
We demonstrate the focusing of a free-space THz beam emerging from a leaky parallel-plate waveguide (PPWG). Focusing is accomplished by grading the launch angle of the leaky wave using a PPWG with gradient plate separation. Inside the PPWG, the phase velocity of the guided TE1 mode exceeds the vacuum light speed, allowing the wave to leak into free space from a slit cut along the top plate. Since the leaky wave angle changes as the plate separation decreases, the beam divergence can be controlled by grading the plate separation along the propagation axis. We experimentally demonstrate focusing of the leaky wave at a selected location at frequencies of 100 GHz and 170 GHz, and compare our measurements with numerical simulations. The proposed concept can be valuable for implementing a flat and wide-aperture beam-former for THz communications systems.
我们展示了从泄漏平行板波导（PPWG）出射的自由空间太赫兹光束的聚焦。通过使用具有渐变板间距的PPWG对泄漏波的发射角进行渐变来实现聚焦。在PPWG内部，被引导的TE1模式的相速度超过真空光速，使得波能够从沿着顶板切割的狭缝泄漏到自由空间中。由于泄漏波角度随着板间距减小而变化，因此可以通过沿传播轴渐变板间距来控制光束发散。我们通过实验证明了在100 GHz和170 GHz频率下在选定位置对泄漏波的聚焦，并将我们的测量结果与数值模拟进行了比较。所提出的概念对于为太赫兹通信系统实现平面宽孔径波束形成器可能具有重要价值。
