Phase Control of Injection-Locked RTD Terahertz Oscillator

We constructed a heterodyne system for measuring the phase of terahertz (THz) waves with high accuracy and achieved to control the phase of a resonant tunneling diode (RTD) oscillator using injection locking. The free-running oscillation frequency of the RTD THz oscillator was tuned from 380.5 to 386.7 GHz in the bias range of 0.61-0.65 V. In the phase measurement, we injected a signal of 383.2 GHz to the RTD THz oscillator and measured the phase with different free-running frequencies. The phase changed almost from −90° to +90° within the locking range, which agrees with the expectation derived from Adler's equation.