We propose a method for the laser-excitation of terahertz surface magnetoplasmons via the linear mode conversion of terahertz radiation on a graphene sheet deposited on an $n$-type semiconductor in the presence of an external magnetic field parallel to the semiconductor surface. An obliquely incident $p$-polarized laser beam interacting with the graphene–$n$-InSb semiconductor surface imparts linear oscillatory velocity to the free electrons. This oscillatory velocity couples with the modulated electron density to generate a linear current density, which resonantly excites terahertz surface magnetoplasmons. It is shown that the amplitude of a terahertz surface magnetoplasmon wave can be tuned by adjusting the external magnetic field $\left({\text{B}}_0\right)$, the graphene's Fermi energy $\left(E_F\right)$, the semiconductor's temperature $\left(T\right)$, and the incident angle $\left(\theta \right)$ of laser. This mechanism has the potential to enable the development of an actively tunable plasmonic device.

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• Terahertz generation in plasmas