Experimental Validation of a Phase Control Concept for Photonically Steered Terahertz Phased Array Transmitters at Microwave Frequencies

Over the last decade, the THz gap is slowly filled in with the rapid improvement of THz sources and detectors. However, low radiation power at higher THz frequencies still limits the variety of applications and remains as a challenge. A phased array transmitter offers a solution to overcome that issue. It can be realized in the optical domain by employing photomixing for terahertz generation and implementing the mature concept of photonic beamforming. However, the fiber based photonic beamforming system may suffer from phase drift that cannot be easily determined due to the lack of phase detection circuitry at terahertz frequencies. In this paper a 4-element phased array with phase control using a lower frequency reference tone is demonstrated and preliminary measurement results at microwave frequencies are presented.