Electrical control of terahertz frequency conversion from time-varying surfaces

Area of Science:

• Terahertz (THz) science and technology
• Optoelectronics
• Metamaterials and Nanophotonics

Background:

• Terahertz (THz) frequency conversion is crucial for THz applications.
• Time-varying surfaces offer novel ways to manipulate THz waves.
• Electrical control provides a pathway for dynamic tuning of THz responses.

Purpose of the Study:

• To investigate the electrical control of frequency conversion using time-varying surfaces.
• To compare the effect of external voltages on interdigitated photo-conductive antennas (IPCAs) and metasurfaces.
• To understand the underlying mechanisms of voltage-induced suppression of THz frequency conversion.

Main Methods:

• Utilizing ultrafast near-infrared (NIR) optical pulses to induce time-varying conductivity.
• Applying external voltages to modulate the conductivity transition speed.
• Analyzing frequency up-conversion and down-conversion processes in both IPCA and metasurface configurations.

Main Results:

• External voltages effectively retard conductivity transitions in both IPCAs and metasurfaces.
• In IPCAs, external voltages suppress both frequency up- and down-conversion.
• In metasurfaces, external voltages dramatically suppress down-conversion while showing less effect on up-conversion.

Conclusions:

• Electrical control offers a viable method for tuning THz frequency conversion.
• The distinct voltage-dependent behaviors of IPCAs and metasurfaces highlight their potential for different THz applications.
• Further research can explore optimized designs for voltage-controlled THz frequency conversion.