Two coupled resonant-tunneling-diode oscillators with an air-bridged transmission line for high-power coherent terahertz radiation

We developed a two-coupled resonant-tunneling-diode (RTD) terahertz (THz) oscillator with a high output power to fill the THz gap. We arranged two RTD mesas in a low-loss air-bridged transmission line for strong mutual coupling and generation of a unique operation mode and integrated a planar ring-slot antenna for efficient THz radiation while satisfying the impedance matching condition. The device structure was fabricated using a multilayer resist process and a carefully controlled wet etching process. The fabricated device exhibited coherent operation and a high output power of approximately 0.24 mW at a high frequency of 925 GHz.