The electromagnetic force in the terahertz band generated by a cross-shaped absorber

• A multi-layered structure which can generate a large electromagnetic force in the terahertz band is proposed.
• The definition of EPD is proposed to prove the force is large enough in the terahertz band.
• The proposed structure is simple and easy for fabrication in the terahertz band.
• Both attractive and propulsive forces can be realized by modifying the refractive index of the dielectric layer.

A 2D periodic force generator in terahertz band is presented. A multi-layered structure is designed, which consists of two adjacent dielectric layers and a cross-shaped metal patch. Once the structure is resonant, strong coupling effect takes place between the two dielectric layers. Due to the coupling effect, the electromagnetic field is enhanced, which leads to a large electromagnetic force. The force is calculated by the Maxwell Stress Tensor. The magnitude of the force is three orders higher than the force generated in the optical band presented in other papers. The power density of the incident light is studied for the demonstration of the usefulness of the force in terahertz band generated by the structure. Dielectric loss is also taken into consideration. The result shows that the magnitude of the force is still enough to offset the gravity of the unit cell even with a high dielectric loss.