Boosting radiation efficiency of photoconductive nano-antennas through 3D light confinement

We present a novel optically-pumped terahertz antenna array, which offers much higher radiation efficiencies compared to the state-of-the-art. The key novelty of the device is tight confinement of the optical pump beam around the antenna elements. The tight light confinement is provided by a specially-designed plasmonic nano-antenna array and photo-absorbing semiconductor substrate, which operates as a reflector. We experimentally demonstrate a record-high pulsed terahertz radiation power of 4 mW and a radiation bandwidth of 0.1-5 THz, exhibiting one order of magnitude enhancement in radiation efficiency compared to the state-of-the-art.