High-power even- and odd-mode emission from linear arrays of resonant-tunneling-diode (RTD) oscillators

Oscillators based on resonant tunneling diodes (RTDs) exhibit the highest oscillation frequency among all electronic THz emitters. However, the emitted power from single RTD oscillators remains limited. Here, we investigate linear RTD oscillator arrays capable of supporting coherent emission from both odd and even coupled modes. Both modes exhibit constructive interference in the far field, enabling high-power emission. Experimental results of coherent emission from linear arrays of 11 RTD oscillators are presented. The odd mode oscillates at approximately 450 GHz, emitting about 0.5 mW of power, while the even mode oscillates at around 750 GHz, emitting at about 1 mW. Moreover, certain RTD-oscillator arrays can oscillate in both modes under different bias voltages, allowing for controllable switching between the even and odd mode. During bias sweeping in both directions, a notable hysteresis feature is observed in the switching behavior of such devices. Our linear RTD oscillator array represents a significant step forward in the realization of large high-power RTD oscillator arrays at high THz frequencies, and will enable novel applications of RTD devices.