Photonic THz emitter with a parasitic-loading patch antenna and a 3D-printed dielectric lens

We experimentally demonstrate a photonic THz emitter that integrates an InGaAs/InP uni-traveling-carrier photodiode (UTC-PD) with a parasitic-loading patch antenna on a high-thermal-conductivity silicon carbide (SiC) substrate. The SiC-substrate-based UTC-PD, fabricated with an advanced wafer-flip bonding technique, leverages the excellent thermal properties of SiC to sustain stable operation at photocurrents up to 10 mA. To expand the operational bandwidth, parasitic patches are employed to achieve a 3 dB bandwidth of 11 GHz centered around 275 GHz. To enhance the radiation characteristics, we integrate a meniscus lens made of low-loss cyclic olefin copolymer and manufactured using a standard desktop 3D printer. Without the lens, the emitter produces a fan-shaped beam with poor directionality, as dictated by the parasitic patch geometry. Lens integration significantly reshapes the beam into a narrow pencil pattern with a measured half-power beamwidth of approximately 10˚ in both E- and H-planes at 275 GHz. This transformation yields an estimated directivity exceeding 26 dBi, driven by a lens-induced gain of approximately 12 dB. The proposed architecture demonstrates that combining photonic emitter technology with low-cost, easily customizable 3D printing enables a practical solution for directive THz radiation. These results offer a compelling path toward lightweight and compact components for next-generation THz wireless systems.