Design and Optimization of High-Impedance Transmission Line Electrode for High-Power and High-Bandwidth Photodetector

Currently, optical communication systems require photodetectors with larger bandwidth and higher output power, and the electrode of the photodetector plays a crucial role in its performance. This paper proposes and adopts a co-simulation method to design an electrode with a high-impedance transmission line to enhance the output power and bandwidth of the photodetector. The co-simulation method can predict the overall bandwidth and output power of the photodetector, continuously optimizing the parameters of the final electrode structure. The high inductance of the high-impedance transmission line, in conjunction with the junction capacitance of the photodetector, results in resonance, boosting the frequency response of the photodetector, increasing the 3dB bandwidth, and making the in-band frequency response flatter.A modified uni-traveling carrier photodetector (MUTC-PD) with a mesa diameter of
$\boldsymbol{20\mu \mathrm{m}}$
is designed, and it is connected to a conventional
$\boldsymbol{50 \Omega}$
impedance transmission line electrode structure, achieving a bandwidth of 48.26GHz. When the same MUTC-PD is connected to the high-impedance transmission line electrode structure, the bandwidth increases to 55.44GHz. At 28GHz and different input optical powers, the output power of the MUTC-PD mounted on the high-impedance transmission line electrode structure is, on average, 8.2% higher compared to the former case.