Active Energy‐Efficient Terahertz Metasurfaces Based on Enhanced In‐Plane Electric Field Density

Abstract Subwavelength confinement of electromagnetic modes in periodic structures is essential to tailor light−matter interaction in space and time. Metamaterials with strong electromagnetic field confinement can be extremely sensitive to surface conditions, thereby enhancing the metadevice response for low‐energy electrical, thermal, and optical stimuli. It is important to note that the total field confinement matters, but the contribution of in‐plane electric field density is critical to efficiently harness and manipulate light via active metasurfaces. The authors experimentally demonstrate a new planar metal–semiconductor hybrid terahertz (THz) metasurface design that shows highly sensitive active THz amplitude modulation towards optical illumination. In the proposed design, in‐plane electric field density has been enhanced by 350% to lower the optical pump fluence requirement for energy‐efficient, active modulation of resonances compared to the conventional inductive‐capacitive resonant metamaterials. Such metasurfaces with large in‐plane electric field density can find many applications in developing ultrasensitive sensors and active THz electrical and optical modulators operational at extremely low energies.