Journal of Theoretical and Applied Physics (JTAP) Improving the terahertz collection efficiency based on impedance matching in spintronic THz emitters Volume 18 (2024) Issue 1, January & February 2024 2023 12 30 Improving the terahertz collection efficiency based on impedance matching in spintronic THz emitters 10.57647/J.JTAP.2024.1801.10 EN Seyedeh Maryam Hosseini Laser and Plasma Research Institute, Shahid Beheshti University, Tehran, Iran Amin Sadraei Javaheri Laser and Plasma Research Institute, Shahid Beheshti University, Tehran, Iran Fazel Jahangiri Laser and Plasma Research Institute, Shahid Beheshti University, Tehran, Iran Seyedeh Mehri Hamidi Laser and Plasma Research Institute, Shahid Beheshti University, Tehran, Iran 0000-0002-5298-2224 Hamid Latifi Laser and Plasma Research Institute, Shahid Beheshti University, Tehran, Iran Journal Article 2023 12 30 We study the improvement of terahertz collection efficiency in a THz-TDS system based on a spintronic THz emitter, by exploring the effect of substrate impedance matching. This improvement is obtained by properly coupling a hyper-hemispherical lens fabricated from suitable THz materials to a non-magnetic (NM)|ferromagnetic (FM)|substrate emitter structure. The emitter is a Ni|Pt bilayer film coated on a MgO substrate. The refractive index and the dispersion properties of the substrate are adjusted according to the impedance matching conditions and consequently for the maximum THz collection efficiency by a photoconductive antenna (PCA). By comparing various substrates, including MgO, Al2O3, SiO2, and polyethylene terephthalate (PET), our results reveal that the power of the THz radiation collected from the Ni|Pt|MgO with the hyper-hemispherical Si-lens coupler is 64.5 times larger than that from the Ni|Pt|MgO without the lens coupler. A PET substrate in direct contact with a hyper-hemispherical Teflon-lens could be a favorable choice for improved collection efficiency of STE-induced THz radiation, in the absence of Si-lens. These results could be considered useful to achieve the guidelines for scaling the THz radiation power emitted from the spintronic THz emitter according to the employed substrate and hyper-hemispherical lens.