Coherent Power Combination in a Resonant-Tunneling-Diode Arrayed Oscillator With Simplified Structure

Coherent resonant-tunneling-diode (RTD) oscillator array is promising for high-power terahertz sources. However, it is complicated to identify the proper operation mode in an arrayed RTD oscillator. Here, we established a simple and general analytical method for operation modes in RTD arrayed oscillators. We also proposed and fabricated a terahertz slot antenna integrated RTD oscillator array coupled by a resistor for stable operation and coherent power combining. From the analysis for the resistor-coupled oscillator array, we found that the odd-mode operation, where adjacent oscillators operate in antiphase condition, is stable. Hence, we proposed an arrayed structure with a right-angle connection between adjacent oscillators for coherent power combination and validation of operation mode. In preliminary experiments, we successfully fabricated two-element resistor-coupled arrayed oscillators. Output power and oscillation spectrum measurements showed that coherent power combination was achieved in arrayed oscillators. The odd-mode operation was validated by polarization measurements. Relatively high output powers of ∼770 μW were obtained at 530 GHz in two-element arrayed oscillators with offset-fed slot antennas.