Magnetoplasmonics Lab

Archives December 8, 2023

Our new paper on THz

Our new Articlein Journal of experimental and theoretical physics

Improving the terahertz collection efficiency based on impedance matching in spintronic THz emitters

S. M. Hosseini, A. Sadraei Javaheri, F. Jahangiri, S. M. Hamidi, H. Latifi

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 of a hyper-hemispherical lens fabricated from suitable THz materials to a nonmagnetic (NM)/ ferromagnetic (FM)/ substrate emitter structure. The emitter is a Ni/Pt bilayer film coated on a MgO substrate. Refractive index and the dispersion properties of the substrate is adjusted according to the impedance matching conditions and consequently for the maximum terahertz detection 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. These results could be considered useful to achieve the guidelines for scaling the terahertz radiation power emitted from the spintronic THz emitter according to the employed substrate and hyper-hemispherical lens.

Fig. 1. Schematic illustration of (a) the THz-TDS experimental setup, and Full top view of a photoconductive antenna chip, as well as, extended top view of the midway placed THz dipole structure only displaying antenna length, gap distance and gap width; STE-induced THz divergence profile (b) without lens attachment as a reference and (c) with the hyper-hemispherical lens attachment on off-axis parabolic mirror; θ is considered cone angle in COMSOL simulation. (d) The dimensions of the hyper-hemispherical lens in accordance with the parameters presented in Table 2.