High-Power MUTC Photodiode Module for Photonics-Assisted Beyond 100 Gb/S Wireless Sub-THZ Communications in the F-Band

Back-illuminated modified uni-traveling carrier photodiode (MUTC-PD) with improved saturation performance at high frequencies is developed and its application in wireless communications is demonstrated. A gradient doped absorption region and a cliff layer with optimized doping concentration are adopted to fine-tune the electric field within the device, so as to alleviate the space-charge screening for high saturation performance. Passive circuits are fabricated on 127-μm-thick quartz substrate for low transmission loss. The fabricated 8-μm-diameter MUTC-PD exhibits flat frequency responses at F-band (90–140 GHz) and high saturation power of 2.3 dBm at 100 GHz. The packaged MUTC-PD module with WR-8 waveguide output serves as a photonics-assisted transmitter for high-performance sub-THz wireless data transmission in the F-band. We have successfully demonstrated a 1-m free space transmission at a carrier frequency of 131.5 GHz. The maximum line rate achieved in our experiment is 120 Gb/s, utilizing 30-Gbaud 16-quadrature amplitude modulation (QAM) signals. Accounting for the overhead of soft-decision forward error correction (SD-FEC), we have achieved a net rate of 104.35 Gb/s for a single channel. Furthermore, a line rate of 100 Gb/s can be maintained for extended distance of free space transmission by simply increasing the input optical power.