Semiconductor THz Emitting Nanometasurface (STEN)

Abstract The direct bandgap semiconductor serves as a fundamental terahertz (THz) source, generating terahertz waves through ultrafast femtosecond light excitation. While the direct bandgap semiconductor THz source does not rely on an external bias voltage, its limited radiation power poses a challenge to its implementation in compact THz systems. Here, nanometasurfaces etched on a semi‐insulating gallium arsenide (GaAs) substrate for enhanced THz emission are reported. The proposed semiconductor terahertz emitting nanometasurface (STEN) device based on GaAs direct bandgap semiconductor shows a 35‐fold increase in THz power and enables precise control of the emitted bandwidth. Giant emission is attributed to the enhanced absorption of pump light by the GaAs nano‐pillar array and the localized effect of the pump field. Experimental results confirm the effectiveness of the structures, demonstrating a negative correlation between the radiation power enhancement factor and pump power, indicating suitability for low‐power sources. This design offers broad prospects for semiconductor THz emitting nanometasurfaces, ideal for integration with compact femtosecond lasers.