UTC-PD-integrated HEMT photonic double-mixers for optical-to-sub-THz/THz carrier-frequency down-conversion in beyond-5G fiber-wireless-convergence networks

We review recent progress in the development of the UTC-PD-integrated HEMT photonic double-mixer as an optical-to-sub-terahertz (THz)/THz carrier-frequency down-converter for use in the future beyond 5G wireless networks. The enhancement of the double-mixing conversion gain up to -39 dB at the 120-GHz band was projected, as well as its operation at the 300-GHz band was experimentally demonstrated. Also, a novel guided-mode-resonance structure embedded into a UTC-PD was proposed for enhancement of the conversion gain.