Theoretical analysis of spectral linewidth of terahertz oscillators using resonant tunneling diodes and their coupled arrays

摘要

The spectral linewidth of terahertz oscillators using resonant tunneling diodes and their coupled arrays is theoretically analyzed. The theoretical linewidths of single oscillators are consistent with the measured results. The linewidth of resonant tunneling diodes is considerably broader than that of terahertz quantum cascade lasers because of lower output power and the existence of shot noise. The theoretical analysis for a single oscillator is extended to a coupled array, and it is shown that the linewidth of a coupled N-element array reduces to 1/N that of a single oscillator, if the frequency deviation among the elements is small. With an increasing frequency deviation, the linewidth increases and exceeds that of a single oscillator. The linewidth also increases with the imaginary part of the coupling admittance between the elements.