Integration of a field-effect-transistor terahertz detector with a diagonal horn antenna

Efficient coupling of terahertz electromagnetic wave with the active region in a terahertz detector is required to enhance the optical sensitivity. In this work, we demonstrate direct integration of a field-effect-transistor (FET) terahertz detector chip at the waveguide port of a horn antenna. Although the integration without a proper backshot is rather preliminary, the noise-equivalent power is greatly reduced from 2.7 nW/Hz^1/2 for the bare detector chip to 76 pW/Hz^1/2 at 340 GHz. The enhancement factor of about 30 is confirmed by simulations revealing the effective increase in the energy flux density seen by the detector. The simulation further confirms the frequency response of the horn antenna and the on-chip antennas. A design with the detector chip fully embedded within a waveguide cavity could be made to further enhance the coupling efficiency.