Generating and Enhancing THz Pulses via an Antenna-Coupled Unitraveling-Carrier Photodiode Array

Terahertz (THz) pulses with picosecond-level duration are generated and enhanced by fabricating arrayed InP/InGaAs unitraveling-carrier photodiodes (UTC-PDs) with integrated planar bowtie antennas. We experimentally demonstrated THz pulses generation from an UTC-PD with a duration of
$10 \,\mathrm{ps}$
and
$25 \,\mathrm{GHz}$
repetition rate. Compared with those of an individual UTC-PD excited at a photocurrent of
$3 \,\mathrm{mA}$
and dc bias voltage of
$-1.5 \,\mathrm{V}$
, the pulsed THz waves generated from three arrayed UTC-PDs exhibited a 7-dB power enhancement gain after optical time alignment through optic-fiber delay lines. Experimental results indicate that this optoelectronic THz pulses generation based on arrayed UTC-PDs can achieve scalable directional gain and low-profile assembly. Enhanced THz pulses generation will be beneficial for the applications of quasi-time-domain THz spectroscope and pulse-based THz communications.