Arrayed uni-traveling-carrier photodiodes for pulsed THz wave beam steering

An electro-optic frequency comb is heterodyne down-converted by a uni-traveling-carrier photodiode (UTC-PD) to a broad spectrum in the range from DC to THz band. As a result, a pulsed THz train with a repetition rate of 25-GHz was generated which is an envelope or averaged intensity of optical pulses. To generate steerable THz pulsed beam, we fabricated a monolithic InP substrate photonics integrated circuit that includes a uniform linear array of four InP/InGaAs UTC-PDs with integrated bow-tie antennas. Concurrently, four variable fiber-optic delay lines were employed in the demonstration setup for altering optical path length (OPL) of the propagating laser pulses in different channels, which eventually resulted in a altered time-delay of the THz pulses. Thus, with a gradient OPL of the laser pulse being adjusted for each UTC-PD, the pulsed THz wave can be continuously steered within a range of 40 degrees at the elevation plane.

Automated summary

An electro-optic frequency comb is down-converted by a uni-traveling-carrier photodiode to generate a pulsed THz train, while a photonics integrated circuit and fiber-optic delay lines are used to alter the time-delay and steer the THz pulsed beam.