Design and Analysis of Waveguide-Coupled Photonic THz Transmitters With an Extremely Wide Fractional Bandwidth

The design and analysis of novel waveguide-coupled photonic transmitters, which can have an extremely wide ±3-dB fractional optical-to-electrical (O-E) bandwidth at near the terahertz (THz) operating frequency regime (100%; 0.1-0.3 THz), are presented. This novel module is composed of a customized WR-10based wideband antenna and an ultrafast/high-power photodiode with a 0.33-THz 3-dB O-E bandwidth, which is flip-chip bonded onto an aluminum nitride substrate, integrated with an impedance matching circuit as well as a bow-tie radiator to serve as the antenna feed. The WR-10-based dual-ridge horn structure is adopted to realize the extremely wideband antenna because the dominant TEM mode supported by the dual ridges has no cutoff frequency. The proposed antenna exhibits more than 18 dB gain across the whole operating bandwidth (0.1-0.3 THz). With the transmitter operating at an output photocurrent of 10 mA and employing the same dual ridge-horn antenna at the receiving end, we can detect a reasonable power (31.6 μW) at 0.24 THz through 1 cm wireless transmission.