Controllable terahertz radiation from electrically tunable plasmonic metasurfaces based on multiple quantum wells.

Area of Science:

• Photonics and Nanotechnology
• Quantum Electronics
• Metamaterials

Background:

• Subwavelength plasmonic metasurfaces integrated with multiple quantum wells (MQWs) enable efficient nonlinear wave generation.
• These systems offer potential for compact, tunable, room-temperature terahertz (THz) wave sources via optical pump mixing and down-conversion.

Purpose of the Study:

• To analyze the electrically controllable THz radiation from a nonlinear metasurface loaded with MQW using the difference frequency generation (DFG) process.
• To demonstrate the electrical tunability of THz beam steering by modulating the nonlinear susceptibility of the MQW.

Main Methods:

• Developed an analytical formulation using the effective nonlinear susceptibility model and free-space Green's function to derive the THz radiation pattern.
• Investigated the phase and amplitude modulation of the second-order nonlinear susceptibility coefficient of MQW by applying varying bias voltages.
• Utilized full-wave analysis to verify the derived far-field directivity pattern of DFG radiation.

Main Results:

• Achieved electrical control over the THz radiation pattern by varying bias voltages applied to the MQW.
• Demonstrated THz beam steering, with the radiation pattern rotating from -20 to 20 degrees.
• Obtained the far-field directivity pattern of DFG radiation at 5.5 THz for a linear array of plasmonic nonlinear metacells.

Conclusions:

• The proposed analytical method provides an effective tool for designing and analyzing electrically tunable nonlinear metasurfaces.
• This technology is promising for future THz applications in wireless communications, spectroscopy, and quantum imaging.
• Electrical control over MQW nonlinear susceptibility enables precise manipulation of THz wave generation and directionality.