Semicircular bow-tie antenna-integrated double waveguide 1.55 µm mushroom photodetectors for cw photonic millimeter wave transmitter modules

In this work, we report on planar antenna-integrated double waveguide 1.55 μm mushroom photodetectors for integration in continuous-wave photonic millimeter wave transmitter modules operating in the complete 30-300 GHz range. For achieving a wide-frequency tuning range, the active photodetector section consisting of a partially p-doped, partially nid-InGaAs absorbing layer is located in a mushroom type optical waveguide for overcoming the compromise between junction capacitance and series resistance. For efficient fiber-chip coupling, a shallow-ridge type passive optical waveguide is used. The photodetector is further monolithically embedded in the applied semicircular bow-tie antenna structure. Thus, an extremely flat frequency response is achieved.