Radiation pattern of planar optoelectronic antennas for broadband continuous- wave terahertz emission

In future wireless communication networks at terahertz frequencies, the directivity and the beam profile of the emitters are highly relevant since no additional beam forming optics can be placed in free-space between the emitter and receiver. We investigated the radiation pattern and the polarization of broadband continuous-wave (cw) terahertz emitters experimentally and by numerical simulations between 100 GHz and 500 GHz. The emitters are indium phosphide (InP) photodiodes with attached planar antenna, mounted on a hyper-hemispherical silicon lens and integrated into a fiber-pigtailed module. As both packaging and material of the emitter was identical for all devices, similarities and differences can be directly linked to the antenna structure. We found that the feeding point structure that connects photodiode and antenna has a large influence on the radiation pattern. By optimizing the feeding point, we could reduce side lobes from -2 dB to -13 dB and narrow the 6dB beam angle from +/- 14 degrees to +/- 9 degrees at 300 GHz. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

In future wireless communication networks at terahertz frequencies, the directivity and beam profile of emitters are crucial, as no additional beam forming optics can be used in free-space. Experimental and numerical investigations showed that the feeding point structure connecting the photodiode and antenna significantly influences the radiation pattern. By optimizing the feeding point, side lobes were reduced from -2 dB to -13 dB and the beam angle was narrowed at 300 GHz.