Optically controlled THz power tuning based on interference at transmission line

We have proposed an optically controlled THz power tuning method based on THz wave interference. Through interfered THz waves at the T-junction transmission line, adjustment of the THz power is achieved, and tuning control is attained by varying the optical time delay of the beat-note lightwaves. To demonstrate and verify THz power tuning with an optical delay line, we have also fabricated a monolithic chip on an InP substrate, which integrates arrayed uni-traveling-carrier photodiodes and a planar slot antenna array for 300GHz wave generation. The experimental results reveal that the power transmission of this THz power tuner can be continuously adjusted with a wider tuning range than 7 dB at 300 GHz band. It should be a promising solution for the integration of compact THz wave planar photonic circuits.