A master voltage controlled oscillator (VCO) produces an output signal at an operating frequency of at least 100 gigaHertz (GHz). A buffer VCO injection-locked to an output of the master VCO produces an output signal at the operating frequency with a voltage swing greater than 50% of an output voltage swing of the master VCO output signal. The buffer VCO operates without pulling, and can drive a load of at least three times greater than a nominal load. Phase noise in the output of the buffer VCO is as much as −96 decibels (dB) relative to the carrier (dBc) per Hertz (Hz) at 125 GHz with a 1 megaHertz (MHz) offset.