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

为了克服现有技术的局限性，我们研究了采用1.56 μ m波长、17 fs抽运脉冲，在脊型波导结构（宽5 μ m、厚3.8 μ m、长10 mm）中，LiNbO3晶体产生THz辐射。太赫兹辐射通过球面硅棱镜耦合输出，增强泵浦光的太赫兹辐射。为了克服这种限制，可以使用相反的几何形状，使得光学和THz波束都入射到天线的接触侧上。然而，挑战在于将太赫兹波聚焦到PCA。为了解决这个问题，我们使用了金属V形槽结构（间隙尺寸约200 μ m），以超聚焦光束超过衍射极限。这种聚焦技术已被证明可以增强基于激光混沌振荡的太赫兹TDS系统中的太赫兹检测强度。

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.