Generation of Intense Monocycle Terahertz Pulse using Tilted Wavefront Technique and its Application : Nonlinear Terahertz Spectroscopy and 3-Dimensional Computed Tomography

Abstract : A novel technique has been demonstrated for the generation of intense terahertz electromagnetic wave that enables high-field near-single-cycle terahertz (THz) pulse via non-collinear χ(2) process in LiNbO3 with both phase-front and spectral angular dispersion. Using this technique we are able to generate a single cycle (broadband) terahertz pulse upto an electric field of 300kV/cm. We measured L-arginine microcrystals pellet in polyethene matrix using this intense THz pulse. With intense incident electric field amplitude, we expected that the large amplitude intermolecular vibration coherently driven which brings nonlinearity. The appearance of such nonlinearity will open new techniques of multi-dimensional spectroscopy and material control. We have also demonstrated the potential of this intense THz pulse for 3D THz imaging. We measured a dynamic range of 619 for the THz detection at the integration time of 10 ms, which is 13- times higher than that of previous system based on collinear optical rectification in ZnTe crystal. The main advantage of the proposed method relies on real-time THz line projection providing 10 ms acquisition time of 2D-ST THz image. Therefore, 3D THz CT has been performed in only 6 minutes, representing a significant improvement compared with common systems. Finally, demonstration of 3D rimages clearly indicated a high potential for sensing, non-destructive inspection and material characterization in real world applications.