A study on ultra broad band terahertz wave generation using nonlinear optical waveguide

为了克服限制，我们研究了各种技术的结合。对于太赫兹辐射，我们展示了在脊型波导结构(宽度5um；厚度3.8um；长度10 mm)中，使用1.56 nm波长、17fs泵浦脉冲的LiNbO_3晶体的产生。利用球面硅棱镜增强泵浦光束的太赫兹辐射，将太赫兹辐射耦合出去。为了克服这一限制，可以使用反向几何结构，使得光学和THz波束都入射到天线的接触侧。然而，挑战是将太赫兹波聚焦到PCA。为了解决这一问题，我们使用了一种金属V型槽结构(间隙尺寸约为200um)来超聚焦超出衍射极限的光束。这种聚焦技术已经被证明提高了基于激光器中混沌振荡的THz-TDS系统中的THz探测强度。

We have studied the combination of state of the art techniques with the aim to overcome limitation.For THz emission, generation from a LiNbO3 crystal in a ridge-type waveguide structure (width 5 um; thickness 3.8 um; length 10 mm) using 1.56 um wavelength, 17 fs pump pulses was demonstrated. The THz radiation was coupled out by a spherical Si prism enhancing the THz radiation from the pump beam. To overcome this limitation, a reverse geometry, so that the optical and the THz beam are both incident onto the contact side of the antenna, can be used. Yet, the challenge is to focus the THz wave to the PCA. To solve this problem, we use a metal V groove structure (gap size about 200 um) to super focus the beam beyond the diffraction limit. This focusing technique has been shown to enhance the intensity of the THz detection in a THz-TDS system based on chaotic oscillation in a laser.