Broadband photonic terahertz-wave emitter integrating uni-traveling-carrier photodiode and self-complementary planar antenna

Two types of photonic terahertz-wave emitters integrating self-complementary planar antennas (a log-periodic antenna or a bowtie antenna) and InP/InGaAs uni-traveling-carrier photodiodes have been fabricated and assembled in compact quasi-optical packages. Although both modules operated at frequencies from ∼150 GHz to 1.6 THz with similar output powers, the one with a log-periodic antenna exhibited a strongly dependent polarization angle of the output signal on frequency. We have found that the behavior in the lowest frequency range can be explained by a resonant mode along the periphery of the antenna by analyzing the resonance frequencies and the polarization angles. In contrast, the module with a bowtie antenna had stable polarization characteristics. The module had a good linearity of the output powers and could be operated even under zero bias conditions. The detected output powers were 59 μW at 350 GHz, 20 μW at 500 GHz, and 3.3 μW at 1 THz for a photocurrent of 10 mA with a bias voltage of only −0.6 V .