Sub-THz Photonic-Transmitters Based on Separated-Transport-Recombination Photodiodes and a Micromachined Slot Antenna

We demonstrate a novel photonic transmitter, which is composed of a low-temperature-grown GaAs (LTG-GaAs)-based separated-transport-recombination photodiode and a micromachined slot antenna. Under femtosecond optical pulse illumination, this device radiates strong electrical pulses (4.5-mW peak power) without the use of a Si-lens. It can be observed in the Fourier transform infrared spectrometer spectrum of radiated pulses that a significant resonance, with a peak power of approximately 300 muW, occurs at 500 GHz, which corresponds to the designed resonant frequency of the slot antenna. The saturation problem related to the output terahertz power that occurs with the traditional LTG-GaAs-based photonic-transmitters when operated under high external applied electrical fields (>50 kV/cm) has been eliminated by the use of our device