Generating and Enhancing THz Pulses via an Antenna-Coupled Unitraveling-Carrier Photodiode Array
Ming Che, Kazuya Kondo, Kazutoshi Kato
Abstract
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10 \,\mathrm{ps}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$25 \,\mathrm{GHz}$</tex-math></inline-formula> repetition rate. Compared with those of an individual UTC-PD excited at a photocurrent of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$3 \,\mathrm{mA}$</tex-math></inline-formula> and dc bias voltage of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-1.5 \,\mathrm{V}$</tex-math></inline-formula> , 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.